Renamed:
MAX_MB_SEGMENTS to MAX_SEGMENTS
MB_SEG_TREE_PROBS to SEG_TREE_PROBS
The minimum unit for segmentation in the segment map
is now 8x8 so it is misleading to use MB_ as macro-block
traditionally refers to a 16x16 region.
Change-Id: I0b55a6f0426bb46dd13435fcfa5bae0a30a7fa22