panfrost: Allow 2D AFBC on Valhall

2D AFBC should be working now, flip the switch. 3D AFBC needs more research to
get right, honestly it's not clear how 3D AFBC on Bifrost is working...

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <!16800>