Fix compile warnings for av1_dist_8x8()
Fix compile warnings for av1_dist_8x8()

Change-Id: I3f3df7acc79f770e42fe65b52f383ee8dfe2702a

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