Adding const to function arguments.

Function list:
  tx_counts_to_branch_counts_32x32
  tx_counts_to_branch_counts_8x8
  tx_counts_to_branch_counts_8x8
  update_ct
  update_ct2
  update_mode_probs

Change-Id: I120d8945a34378cf285d6bd415e23de1d522cf2f
2 files changed