When attempting to normalize function names to end in Row_SIMD it was made
harder with MIPS_DSPR2 naming convention.
Other CPUs do not include the vendor.  This should be named consistently.

Removed the DISABLE_MIPS in favour of DISABLE_ASM for consistency with other
processors.

TBR=harryjin@google.com
BUG=libyuv:562

Review URL: https://codereview.chromium.org/1677633002 .