Adding TREE_SIZE macro + cleanup.

Using TREE_SIZE for the following trees:
  vp9_intra_mode_tree
  vp9_inter_mode_tree
  vp9_partition_tree
  vp9_switchable_interp_tree
  vp9_mv_joint_tree
  vp9_mv_class_tree
  vp9_mv_class0_tree
  vp9_mv_fp_tree

Change-Id: I0212bb4c1ee6648249f68517e28a67a56591ee1b
5 files changed