MIPS: Optimize DoCheckMaps.

This simple change moves the Deoptimize call into the Deopt table
where it belongs, and shortens the inline map-check.

Gives a surprisingly large performance gain, around 4% on Octane.

BUG=
R=gergely@homejinni.com

Review URL: https://codereview.chromium.org/22391008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16115 ce2b1a6d-e550-0410-aec6-3dcde31c8c00