Revert of Fix clobbered register when setting this_function variable.

src/mips/full-codegen-mips.cc

Index: src/mips/full-codegen-mips.cc
diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index e6fee96d35d066e4aea276aa24f330237a0a87ef..2440f9838362534dd70a472b133c2670b92824a7 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -252,10 +252,6 @@
   Variable* this_function_var = scope()->this_function_var();
   if (this_function_var != nullptr) {
     Comment cmnt(masm_, "[ This function");
-    if (!function_in_register) {
-      __ lw(a1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
-      function_in_register = true;
-    }
     SetVar(this_function_var, a1, a2, a3);
   }