ARM: clean up code now that ARMv6 is the baseline.

BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com/14188016

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14325 ce2b1a6d-e550-0410-aec6-3dcde31c8c00