This takes hw constraints specific to pixel formats into account,
e.g., the inability of older hw to scale fp16 format framebuffers.

It should now allow safely to enable fp16 formats also on DCE-8,
DCE-10, DCE-11.0
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>