Implement fidentity{8/16}_new_sse2
Implement fidentity{8/16}_new_sse2

Change-Id: I2cd5eca68eada9053a229e11e364187e923cbd64

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