MIPS: Fix LFastLiteral to check boilerplate elements kind.

MIPS: Fix LFastLiteral to check boilerplate elements kind.

Port r11470 (621f96c0)

Original commit message:
Fix LFastLiteral to check boilerplate elements kind.

Adds a missing check that the elements kind of the boilerplate object
still has the expected elements kind, unoptimized code can transition
the boilerplate. Corner cases might cause the optimized code to be
reentered again.

BUG=
TEST=

Committed: https://code.google.com/p/v8/source/detail?r=11474

[Michael Starzinger, 2012-05-02 09:37:19]

LGTM (although untested because MIPS doesn't compile ATM). Landed.