drm/amd/display: Check DP Alt mode DPCS state via DMUB

[Why]
Currently, driver state for DCN3.2 is not strictly matching HW state for
the USBC port. To reduce inconsistencies while debugging, the driver
should match HW configuration.

[How]
Update link encoder flag to indicate USBC port. Call into DMUB to check
when DP Alt mode is entered, and also to check for 2-lane versuse 4-lane
mode.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>