[Why & How]
We'll need these in driver for phy tuning in DCN3.1.

Multiple eDP support also requires understanding which LCD the backlight
curve in atombios is for.
Acked-by: NHuang Rui <ray.huang@amd.com>
Signed-off-by: NNicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>