X87: Use a register spec for StoreIC and KeyedStoreIC.

port r22328

original commit message:

  Use a register spec for StoreIC and KeyedStoreIC.

  This continues refactoring already applied for LoadIC in r22035 (https://code.google.com/p/v8/source/detail?r=22035).

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/382123003

Patch from Chunyang Dai <chunyang.dai@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22343 ce2b1a6d-e550-0410-aec6-3dcde31c8c00