Fix the comments.

Change-Id: I9789476865a1b24dad54115d8f7edb4fed780b90
Fix for crash in highbitdepth rt mode

Change 72141 introduced a new use of vp9_avg_4x4.
This call needs to switch to using vp9_highbd_avg_4x4
when performing high bitdepth encodes.

Change-Id: I6a8ba4b62f8a75d0a917b365a55245e2f0438ea1
Merge "Fix the comments."
Merge "Fix for crash in highbitdepth rt mode"