drm/amd/display: Use the correct input TF for video formats

[Why]
Color blending for NV12 formats is incorrect because we're using the
predefined SRGB degamma.

[How]
Calculate the correct input transfer function for degamma from the color
module depending on what the actual surface format is.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Zhan Liu <Zhan.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>