When allocating betacb for a GfxP channel, add both alpha and beta
cb sizes together.
Change-Id: I8cef62f6272bfb3b5e9a3835a51590e5eb91dc92
Signed-off-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-on: http://git-master/r/752633
Reviewed-by: Automatic_Commit_Validation_User