MIPS: Fix test262 regression.

This regression was introduced by r13705 (fd03c7d6)

BUG=test262/data/test/suite/ch11/11.13/11.13.2

Review URL: https://codereview.chromium.org/12844005
Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13944 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -1268,12 +1268,12 @@ void LCodeGen::DoMulI(LMulI* instr) {
             __ sll(result, left, shift);
           } else if (IsPowerOf2(constant_abs - 1)) {
             int32_t shift = WhichPowerOf2(constant_abs - 1);
-            __ sll(result, left, shift);
-            __ Addu(result, result, left);
+            __ sll(scratch, left, shift);
+            __ Addu(result, scratch, left);
           } else if (IsPowerOf2(constant_abs + 1)) {
             int32_t shift = WhichPowerOf2(constant_abs + 1);
-            __ sll(result, left, shift);
-            __ Subu(result, result, left);
+            __ sll(scratch, left, shift);
+            __ Subu(result, scratch, left);
           }
 
           // Correct the sign of the result is the constant is negative.