Fix intra boundary condition in ext-partition
Fix intra boundary condition in ext-partition

Make the intra prediction boundary condition account for the
64x64 processing unit constraint. This avoids a rare enc/dec
mismatch issue in 128x128 intra coded block.

Change-Id: Idb05cae8b17ae94c7a4e49e5d58b5865e5fc2f7d

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