[flang] Support fir.llvm_ptr in getTypeAsString

flang/lib/Optimizer/Dialect/FIRType.cpp

if (fir::isa_trivial(ty)) {
       }
       ty = seqTy.getEleTy();
     } else if (auto refTy = mlir::dyn_cast_or_null<fir::ReferenceType>(ty)) {
       name << "ref_";
       ty = refTy.getEleTy();
     } else if (auto ptrTy = mlir::dyn_cast_or_null<fir::PointerType>(ty)) {
       name << "ptr_";
       ty = ptrTy.getEleTy();
+    } else if (auto ptrTy = mlir::dyn_cast_or_null<fir::LLVMPointerType>(ty)) {
+      name << "llvmptr_";
+      ty = ptrTy.getEleTy();
     } else if (auto heapTy = mlir::dyn_cast_or_null<fir::HeapType>(ty)) {
       name << "heap_";
       ty = heapTy.getEleTy();
     } else if (auto classTy = mlir::dyn_cast_or_null<fir::ClassType>(ty)) {
       name << "class_";
       ty = classTy.getEleTy();
     } else if (auto boxTy = mlir::dyn_cast_or_null<fir::BoxType>(ty)) {
       name << "box_";

flang/unittests/Optimizer/FIRTypesTest.cpp

TEST_F(FIRTypesTest, getTypeAsString) {
   components.emplace_back("p1", mlir::IntegerType::get(&context, 64));
   derivedTy.finalize({}, components);
   EXPECT_EQ("rec_derived", fir::getTypeAsString(derivedTy, *kindMap));
   mlir::Type dynArrTy =
       fir::SequenceType::get({fir::SequenceType::getUnknownExtent(),
                                  fir::SequenceType::getUnknownExtent()},
           ty);
   EXPECT_EQ("?x?xi64", fir::getTypeAsString(dynArrTy, *kindMap));
+  EXPECT_EQ("llvmptr_i32",
+      fir::getTypeAsString(
+          fir::LLVMPointerType::get(mlir::IntegerType::get(&context, 32)),
+          *kindMap));
 }