MIPS: Remove HCheckSmi, LCheckSmi and rename LCheckSmiAndReturn to LCheckSmi.

Port r14816 (0485153d)

BUG=

Review URL: https://codereview.chromium.org/16035008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14823 ce2b1a6d-e550-0410-aec6-3dcde31c8c00