avcodec/mips/h264chroma_mmi: Version 2 of the optimizations for loong…

…son mmi

1. no longer use the register names directly and optimized code format
2. to be compatible with O32, specify type of address variable with mips_reg and handle the address variable with PTR_ operator
3. use uld and mtc1 to workaround cpu 3A2000 gslwlc1 bug (gslwlc1 instruction extension bug in O32 ABI)

Signed-off-by: Michael Niedermayer <[email protected]>