Support 2x2 scan order in ext-tx
Support 2x2 scan order in ext-tx

Change-Id: I6ff6916a76a1ebbd964ececb1d81e9df59234d92

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