selfguided_restoration_avx2 memsets optimization
selfguided_restoration_avx2 memsets optimization

Excessive memset removed from
av1_selfguided_restoration_avx2,
replaced with a special avx func in
integral_images_highbd and integral_images
Resulting decoding performance increase - 2-5%

Change-Id: I0f2d655bb0ac9c154ccfa5b80a8f645ffc770625

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom