MIPS: Do not use CodeStub::FindInCache if not necessary.

Port r23795 (b41f4a7)

Original commit message:
GetCode does the FindInCache check as well.

BUG=
R=akos.palfi@imgtec.com, dusan.milosavljevic@imgtec.com

Review URL: https://codereview.chromium.org/549403004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23807 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
[turbofan] ARM64 branch selector additions

Add support for selecting Cmp and Cmn instructions, and tests for branching on
the result of arithmetic or logical operations.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/556823002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23808 ce2b1a6d-e550-0410-aec6-3dcde31c8c00