MIPS: Fix packed-element.js test on ARM with no snap

Port r11826 (5be3568a)

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10559002
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11840 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/macro-assembler-mips.cc

@@ -4459,7 +4459,8 @@ void MacroAssembler::LoadTransitionedArrayMapConditional(
                 Context::SlotOffset(Context::JS_ARRAY_MAPS_INDEX)));
   size_t offset = expected_kind * kPointerSize +
       FixedArrayBase::kHeaderSize;
-  Branch(no_map_match, ne, map_in_out, Operand(scratch));
+  lw(at, FieldMemOperand(scratch, offset));
+  Branch(no_map_match, ne, map_in_out, Operand(at));
 
   // Use the transitioned cached map.
   offset = transitioned_kind * kPointerSize +