drm/amd/display: correct type mismatches in comparisons in DML2

drm/amd/display: correct type mismatches in comparisons in DML2

[Why]
Comparisons were made between unsigned char and unsigned int.

[How]
Corrected by changing variable types.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Natanel Roizenman <Natanel.Roizenman@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>