Logging DCN3 MPC state was following DCN1 implementation that doesn't
consider new DCN3 MPC color blocks. Create new elements according to
DCN3 MPC color caps and a new DCN3-specific function for reading MPC
data.

v3:
- remove gamut remap reg reading in favor of fixed31_32 matrix data
Signed-off-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>