Make ALT_INTRA work with CB4X4.
Make ALT_INTRA work with CB4X4.

Change-Id: Ibc1803c3d149c6a53d1817798d0cab6dc5ab5927

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