drm/i915/dsc: Add helper to enable the DSC configuration for a CRTC

drm/i915/dsc: Add helper to enable the DSC configuration for a CRTC

Add a helper to enable the DSC compression configuration for a CRTC.
Follow-up changes will introduce tracking for the same DSC state on the
whole link, which will need to be set whenever DSC is enabled for the
CRTC. Also, according to the above, when querying the DSC state on the
link, both the CRTC's and the link's DSC state must be considered.

Setting the DSC configuration for a CRTC and querying the DSC
configuration for the link (added by follow-up changes) is better done
via helper functions based on the above, prepare for that here.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://lore.kernel.org/r/20251015161934.262108-2-imre.deak@intel.com