Optimize vp8 loop filter with mmi, four functions optimized: 1. ff_vp8_h_loop_filter8uv_mmi. 2. ff_vp8_v_loop_filter8uv_mmi. 3. ff_vp8_h_loop_filter16_mmi. 4. ff_vp8_v_loop_filter16_mmi. Vp8 decoding speed improved about 50%(from 73fps to 110fps, Tested on loongson 3A3000). Signed-off-by: Shiyou Yin <yinshiyou-hf@loongson.cn> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>