drm/amd/display: Add DSC 422Native debug option

[Why]
Need to be able to enable native 422 for debugging purposes.

[How]
Add new dc_debug_options bool and check it in the get_dsc_enc_caps
function.

Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>