[mlir][OpenMP][NFC] Remove unnecessary attributes

[shraiysh]

Summary

These attributes were added because of oilist required them earlier. It
no longer requires them and so these attributes can be safely removed
from the operations.

[kiranchandramohan]

LGTM.

mlir/test/Dialect/OpenMP/ops.mlir

 func @omp_parallel(%data_var : memref<i32>, %if_cond : i1, %num_threads : si32) -> () {
   // CHECK: omp.parallel if(%{{.*}}) num_threads(%{{.*}} : si32) allocate(%{{.*}} : memref<i32> -> %{{.*}} : memref<i32>)
   "omp.parallel" (%if_cond, %num_threads, %data_var, %data_var) ({
 
   // test without if condition
   // CHECK: omp.parallel num_threads(%{{.*}} : si32) allocate(%{{.*}} : memref<i32> -> %{{.*}} : memref<i32>)
     "omp.parallel"(%num_threads, %data_var, %data_var) ({
       omp.terminator
-    }) {num_threads, allocate, operand_segment_sizes = dense<[0,1,1,1]>: vector<4xi32>} : (si32, memref<i32>, memref<i32>) -> ()
+    }) {operand_segment_sizes = dense<[0,1,1,1]>: vector<4xi32>} : (si32, memref<i32>, memref<i32>) -> ()
 
   // CHECK: omp.barrier
     omp.barrier
 
   // test without num_threads
   // CHECK: omp.parallel if(%{{.*}}) allocate(%{{.*}} : memref<i32> -> %{{.*}} : memref<i32>)
     "omp.parallel"(%if_cond, %data_var, %data_var) ({
       omp.terminator
-    }) {if, allocate, operand_segment_sizes = dense<[1,0,1,1]> : vector<4xi32>} : (i1, memref<i32>, memref<i32>) -> ()
+    }) {operand_segment_sizes = dense<[1,0,1,1]> : vector<4xi32>} : (i1, memref<i32>, memref<i32>) -> ()
 
   // test without allocate
   // CHECK: omp.parallel if(%{{.*}}) num_threads(%{{.*}} : si32)
     "omp.parallel"(%if_cond, %num_threads) ({
       omp.terminator
-    }) {if, num_threads, operand_segment_sizes = dense<[1,1,0,0]> : vector<4xi32>} : (i1, si32) -> ()
+    }) {operand_segment_sizes = dense<[1,1,0,0]> : vector<4xi32>} : (i1, si32) -> ()
 
     omp.terminator
-  }) {if, num_threads, allocate, operand_segment_sizes = dense<[1,1,1,1]> : vector<4xi32>, proc_bind_val = #omp<"procbindkind spread">} : (i1, si32, memref<i32>, memref<i32>) -> ()
+  }) {operand_segment_sizes = dense<[1,1,1,1]> : vector<4xi32>, proc_bind_val = #omp<"procbindkind spread">} : (i1, si32, memref<i32>, memref<i32>) -> ()
 
   // test with multiple parameters for single variadic argument
   // CHECK: omp.parallel allocate(%{{.*}} : memref<i32> -> %{{.*}} : memref<i32>)
   "omp.parallel" (%data_var, %data_var) ({
     omp.terminator
-  }) {allocate, operand_segment_sizes = dense<[0,0,1,1]> : vector<4xi32>} : (memref<i32>, memref<i32>) -> ()
+  }) {operand_segment_sizes = dense<[0,0,1,1]> : vector<4xi32>} : (memref<i32>, memref<i32>) -> ()
 
   return
 }
 
 func @omp_parallel_pretty(%data_var : memref<i32>, %if_cond : i1, %num_threads : si32, %allocator : si32) -> () {
  // CHECK: omp.parallel
  omp.parallel {
   omp.terminator

 // CHECK-LABEL: omp_target
 func @omp_target(%if_cond : i1, %device : si32,  %num_threads : si32) -> () {
 
     // Test with optional operands; if_expr, device, thread_limit, private, firstprivate and nowait.
     // CHECK: omp.target if({{.*}}) device({{.*}}) thread_limit({{.*}}) nowait
     "omp.target"(%if_cond, %device, %num_threads) ({
        // CHECK: omp.terminator
        omp.terminator
-    }) {if, device, nowait, operand_segment_sizes = dense<[1,1,1]>: vector<3xi32>, thread_limit} : ( i1, si32, si32 ) -> ()
+    }) {nowait, operand_segment_sizes = dense<[1,1,1]>: vector<3xi32>} : ( i1, si32, si32 ) -> ()
 
     // CHECK: omp.barrier
     omp.barrier
 
     return
 }
 
 // CHECK-LABEL: omp_target_pretty

 
 // CHECK-LABEL: omp_sectionsop
 func @omp_sectionsop(%data_var1 : memref<i32>, %data_var2 : memref<i32>,
                      %data_var3 : memref<i32>, %redn_var : !llvm.ptr<f32>) {
   // CHECK: omp.sections allocate(%{{.*}} : memref<i32> -> %{{.*}} : memref<i32>)
   "omp.sections" (%data_var1, %data_var1) ({
     // CHECK: omp.terminator
     omp.terminator
-  }) {allocate, operand_segment_sizes = dense<[0,1,1]> : vector<3xi32>} : (memref<i32>, memref<i32>) -> ()
+  }) {operand_segment_sizes = dense<[0,1,1]> : vector<3xi32>} : (memref<i32>, memref<i32>) -> ()
 
     // CHECK: omp.sections reduction(@add_f32 -> %{{.*}} : !llvm.ptr<f32>)
   "omp.sections" (%redn_var) ({
     // CHECK: omp.terminator
     omp.terminator
-  }) {reduction, operand_segment_sizes = dense<[1,0,0]> : vector<3xi32>, reductions=[@add_f32]} : (!llvm.ptr<f32>) -> ()
+  }) {operand_segment_sizes = dense<[1,0,0]> : vector<3xi32>, reductions=[@add_f32]} : (!llvm.ptr<f32>) -> ()
 
   // CHECK: omp.sections nowait {
   omp.sections nowait {
     // CHECK: omp.terminator
     omp.terminator
   }
 
   // CHECK: omp.sections reduction(@add_f32 -> %{{.*}} : !llvm.ptr<f32>) {