MIPS: Small fix for r11771 (1b74d45b).

TEST=mjsunit/object-define-property.js

BUG=

Review URL: https://chromiumcodereview.appspot.com/10535138
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11787 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/stub-cache-mips.cc

@@ -2702,7 +2702,7 @@ Handle<Code> StoreStubCompiler::CompileStoreViaSetter(
                       CALL_AS_METHOD);
 
     // We have to return the passed value, not the return value of the setter.
-    __ pop(a0);
+    __ pop(v0);
 
     // Restore context register.
     __ lw(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));