X87: Use the same registers for StoreIC and KeyedStoreIC.

port r22387

original commit message:
  Use the same registers for StoreIC and KeyedStoreIC.

  Based on https://codereview.chromium.org/389283002 ("Use register parameters in ElementsTransitionGenerator") which must land first.

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/391933002

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

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22405 ce2b1a6d-e550-0410-aec6-3dcde31c8c00