drm/amd/display: Add DCN3.1 PANEL

The PANEL block handles embedded panel power and backlight programming.

This programming and sequencing is now owned by DMCUB and driver will
call into the interface for backlight status and programming.

Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>