Program correct CB size for GfxP channels. We were accidentally using the context image size. Change-Id: I273215256e41e89b7d76f3294a73641804beeb79 Signed-off-by: Terje Bergstrom <tbergstrom@nvidia.com> Reviewed-on: http://git-master/r/792713 Reviewed-on: http://git-master/r/806188