Simplify the usage of intermediate variable addr and remove unused variable all64
in following functions:
1. ff_put_pixels_clamped_mmi
2. ff_put_signed_pixels_clamped_mmi
3. ff_add_pixels_clamped_mmi

This optimization speed up mpeg4 decode about 2% on loongson platform(tested with 3A3000).
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1.MMI_ load/store macros are defined in libavutil/mips/mmiutils.h
2.Replace some unnecessary unaligned access with aligned operator
3.The MMI_ load/store is compatible with cpu loongson2e/2f which not support instructions start with gs
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

    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
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Signed-off-by: ZhouXiaoyong <zhouxiaoyong@loongson.cn>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Signed-off-by: ZhouXiaoyong <zhouxiaoyong@loongson.cn>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>