drm/amd/display: Set ODM policy based on number of DSC slices

[Why & How]
Add addtional check in CalculateODMMode for cases where the ODM combine
is needed due to number of DSC slices.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Brian Chang <Brian.Chang@amd.com>
Signed-off-by: Taimur Hassan <Syed.Hassan@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>