MIPS: Fix register usage after r21822.

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index f1c7b9a6c805f22ee5854656d45b6248fcbd979d..5edca6a39197e06aa8b87518438a258702ae01db 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -1341,7 +1341,7 @@ void LCodeGen::DoFlooringDivByPowerOf2I(LFlooringDivByPowerOf2I* instr) {
   __ Xor(scratch, scratch, result);
   if (divisor == -1) {
     if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
-      DeoptimizeIf(ge, instr->environment(), at, Operand(zero_reg));
+      DeoptimizeIf(ge, instr->environment(), scratch, Operand(zero_reg));
     }
     return;
   }