Set spatial neighbor search resolution 16x16 for block size 64x64
Set spatial neighbor search resolution 16x16 for block size 64x64

When the block has width/height above or equal to 64, use 16x16
block search step for reference motion vector search in the non-
immediate rows and columns.

Change-Id: Ica0cb9990bf6c31cfdded255558dafe0743d8062

luctrudeau/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom,luctrudeau/aom,smarter/aom,smarter/aom,mbebenita/aom,GrokImageCompression/aom,smarter/aom,mbebenita/aom,mbebenita/aom,GrokImageCompression/aom,mbebenita/aom,mbebenita/aom,smarter/aom,mbebenita/aom,smarter/aom,GrokImageCompression/aom,mbebenita/aom,smarter/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,luctrudeau/aom,luctrudeau/aom,GrokImageCompression/aom