[cleanup] Merge DefineAsConstant functions

Change-Id: I9e9cc357cdadf81e8689b54626cff5ccdda2aa41
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1700437Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62693}

src/compiler/backend/instruction-selector-impl.h

@@ -109,13 +109,9 @@ class OperandGenerator {
   }
 
   InstructionOperand DefineAsConstant(Node* node) {
-    return DefineAsConstant(node, ToConstant(node));
-  }
-
-  InstructionOperand DefineAsConstant(Node* node, Constant constant) {
     selector()->MarkAsDefined(node);
     int virtual_register = GetVReg(node);
-    sequence()->AddConstant(virtual_register, constant);
+    sequence()->AddConstant(virtual_register, ToConstant(node));
     return ConstantOperand(virtual_register);
   }