MIPS: Fix Kraken gaussian blur test regression.

The regression was introduced in r13848 by accidental removal of one
additional line.

TEST=
BUG=

Review URL: https://codereview.chromium.org/17570007
Patch from Dusan Milosavljevic <Dusan.Milosavljevic@rt-rk.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15303 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -3627,6 +3627,7 @@ void LCodeGen::EmitIntegerMathAbs(LMathAbs* instr) {
   Label done;
   __ Branch(USE_DELAY_SLOT, &done, ge, input, Operand(zero_reg));
   __ mov(result, input);
+  __ subu(result, zero_reg, input);
   // Overflow if result is still negative, i.e. 0x80000000.
   DeoptimizeIf(lt, instr->environment(), result, Operand(zero_reg));
   __ bind(&done);