MIPS: port Fix ARM regression introduced with polymorphic array support.

Ported r8484 (9f824d7)

BUG=
TEST=

Review URL: http://codereview.chromium.org//7237046
Patch from Paul Lind <plind44@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8570 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/macro-assembler-mips.cc

@@ -2804,7 +2804,7 @@ void MacroAssembler::CheckFastElements(Register map,
                                        Register scratch,
                                        Label* fail) {
   STATIC_ASSERT(JSObject::FAST_ELEMENTS == 0);
-  lbu(scratch, FieldMemOperand(map, Map::kInstanceTypeOffset));
+  lbu(scratch, FieldMemOperand(map, Map::kBitField2Offset));
   Branch(fail, hi, scratch, Operand(Map::kMaximumBitField2FastElementValue));
 }