mips32/mips64: rename mips32_features to mips_features

As this file is now detecting mips64/Cavium boards, we are renaming it to
reflect that. The functional change is that mips_features now can detect
Cavium board and allow Cavium-specific tests to be run.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13551 a5019735-40e9-0310-863c-91ae7b9d1cf9