MIPS: Fix register clobbering in LoadIC for interceptors.

MIPS: Fix register clobbering in LoadIC for interceptors.

Port r11492 (d14ada19)

Original commit message:
Fix register clobbering in LoadIC for interceptors.

This fixes a corner-case where the receiver register was clobbered by
LoadICs for interceptors and inlined followup code still relied on the
receiver to be intact in case of prototype changes.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10315016
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11506 ce2b1a6d-e550-0410-aec6-3dcde31c8c00