drm/amd/display: Flattening to dc_transfer_func

Flattening dc transfer functions in the following manner:
transfer_func > core_transfer_func > dc_transfer_func

References to deleted structs are updated as needed.

Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>