drm/i915/dp: Make sure the DSC PPS SDP is disabled whenever DSC is disabled

Atm the DSC PPS SDP will stay enabled after enabling and disabling DSC.
This leaves an output blank after switching off DSC on it. Make sure the
SDP is disabled for an uncompressed output.

v2:
- Disable the SDP already during output disabling. (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231030155843.2251023-17-imre.deak@intel.com