drm/i915/dp: Fix connector DSC HW state readout

drm/i915/dp: Fix connector DSC HW state readout

The DSC HW state of DP connectors is read out during driver loading and
system resume in intel_modeset_update_connector_atomic_state(). This
function is called for all connectors though and so the state of DSI
connectors will also get updated incorrectly, triggering a WARN there
wrt. the DSC decompression AUX device.

Fix the above by moving the DSC state readout to a new DP connector
specific sync_state() hook. This is anyway the logical place to update
the connector object's state vs. the connector's atomic state.

Fixes: b2608c6b3212 ("drm/i915/dp_mst: Enable MST DSC decompression for all streams")
Reported-and-tested-by: Drew Davenport <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]
Reviewed-by: Ankit Nautiyal <[email protected]>
Signed-off-by: Imre Deak <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit a62e145981500996ea76af3d740ce0c0d74c5be0)
Signed-off-by: Joonas Lahtinen <[email protected]>