drm/amd/display: Enable fp16 also on DCE-8/10/11.

The hw supports fp16, this is not only useful for HDR,
but also for standard dynamic range displays, because
it allows to get more precise color reproduction with
about 11 - 12 bpc linear precision in the unorm range
0.0 - 1.0.

Working fp16 scanout+display (and HDR over HDMI) was
verified on a DCE-8 asic, so i assume that the more
recent DCE-10/11 will work equally well, now that
format-specific plane scaling constraints are properly
enforced, e.g., the inability of fp16 to scale on older
hw like DCE-8 to DCE-11.

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>