MIPS optimizations for AEC audio processing module

The resulting output streams obtained by testing with audioproc test application
are bit-exact with generic C code output streams.

Performance gain achieved:
- mips32 ~ 17%
- mips32r2 ~ 20%
- mipsdsp & mipsdspr2 ~ 21%

R=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/7359004

Patch from Ljubomir Papuga <lpapuga@mips.com>.

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5591 4adac7df-926f-26a2-2b94-8c16560cd09d
8 files changed