avcodec/h264: enable sse2 chroma deblock/loop filter functions

Between 1.00 and 1.16 times faster on Intel Yorkfield Core 2 Quad.
Between 1.11 and 1.39 times faster on Intel Kaby Lake Pentium.

libavcodec/x86/h264_deblock.asm

@@ -1252,6 +1252,7 @@ RET
 
 %endmacro ; DEBLOCK_CHROMA_XMM
 
+DEBLOCK_CHROMA_XMM sse2
 DEBLOCK_CHROMA_XMM avx
 
 ;-----------------------------------------------------------------------------

libavcodec/x86/h264dsp_init.c

@@ -304,6 +304,16 @@ av_cold void ff_h264dsp_init_x86(H264DSPContext *c, const int bit_depth,
 #if ARCH_X86_64
             c->h264_h_loop_filter_luma_mbaff = ff_deblock_h_luma_mbaff_8_sse2;
 #endif
+
+            c->h264_v_loop_filter_chroma       = ff_deblock_v_chroma_8_sse2;
+            c->h264_v_loop_filter_chroma_intra = ff_deblock_v_chroma_intra_8_sse2;
+            if (chroma_format_idc <= 1) {
+                c->h264_h_loop_filter_chroma       = ff_deblock_h_chroma_8_sse2;
+                c->h264_h_loop_filter_chroma_intra = ff_deblock_h_chroma_intra_8_sse2;
+            } else {
+                c->h264_h_loop_filter_chroma       = ff_deblock_h_chroma422_8_sse2;
+                c->h264_h_loop_filter_chroma_intra = ff_deblock_h_chroma422_intra_8_sse2;
+            }
         }
         if (EXTERNAL_SSSE3(cpu_flags)) {
             c->biweight_h264_pixels_tab[0] = ff_h264_biweight_16_ssse3;