Account for sub8x8 chroma intra boundary condition

Properly account for the intra boundary condition for sub8x8
chroma components in the modified chroma-2x2 framework. This fixes
a rare enc/dec mismatch issue when chroma-sub8x8 is turned on.

Change-Id: I058a2fb855a491bf604277f4c82169c1b55424fa
3 files changed