drm/amd/display: remove dmcub_support cap dependency

[why]
matching the dmcub_support with all other dcn version.

Reviewed-by: Sung joon Kim <Sungjoon.Kim@amd.com>
Reviewed-by: Martin Leung <Martin.Leung@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>