Avoid one branch in Operation::getOpOperand()/getOperand() (NFC)

[mehdi_amini]

Summary

Skip the check on "hasOperandStorage" since the array will be indexed anyway.

mlir/include/mlir/IR/Operation.h

public:
   /// Returns an iterator on the underlying Value's.
   operand_range getOperands() { return operand_range(this); }
 
   MutableArrayRef<OpOperand> getOpOperands() {
     return LLVM_LIKELY(hasOperandStorage) ? getOperandStorage().getOperands()
                                           : MutableArrayRef<OpOperand>();
   }
 
-  OpOperand &getOpOperand(unsigned idx) { return getOpOperands()[idx]; }
+  OpOperand &getOpOperand(unsigned idx) {
+    return getOperandStorage().getOperands()[idx];
+  }
 
   // Support operand type iteration.
   using operand_type_iterator = operand_range::type_iterator;
   using operand_type_range = operand_range::type_range;
   operand_type_iterator operand_type_begin() { return operand_begin(); }
   operand_type_iterator operand_type_end() { return operand_end(); }
   operand_type_range getOperandTypes() { return getOperands().getTypes(); }