drm/amd/display: decouple steps for mapping CRTC degamma to DC plane

drm/amd/display: decouple steps for mapping CRTC degamma to DC plane

The next patch adds pre-blending degamma to AMD color mgmt pipeline, but
pre-blending degamma caps (DPP) is currently in use to provide DRM CRTC
atomic degamma or implict degamma on legacy gamma. Detach degamma usage
regarging CRTC color properties to manage plane and CRTC color
correction combinations.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>