drm/i915/dp: Flush modeset commits during connector detection

drm/i915/dp: Flush modeset commits during connector detection

Make sure that a DP connector detection doesn't happen in parallel
with an ongoing modeset on the connector. The reasons for this are:

- Besides reading the capabilities, EDID etc. the detection may change
  the state of the sink (via the AUX bus), for instance by setting the
  LTTPR mode or the source OUI (the latter introduced by an upcoming
  patch). It's better to avoid such changes affecting an onging modeset
  in any way.

- During a modeset's link training any access to DPCD registers, besides
  the registers used for link training should be avoided, at least in
  the LTTPR non-transparent and transparent link training modes.

  Such asynchronous accesses - besides connector detection - can also
  happen via the AUX device node for instance, for those a parallel
  modeset will have to be avoided in a similar way to the change in this
  patch. (A topic for a follow-up change.)

- The source OUI written to an eDP sink is valid only while the panel
  power is enabled. A modeset on eDP will enable/disable the panel power
  synchronously; this should be prevented in the middle of the connector
  detection, to ensure a consistent sink state (which depends on the
  source OUI) for the whole duration of detection. The panel power could
  still get disabled during detection after an idle period (1 sec), this
  will be prevented by the next patch.

v2: (Ville)
- s/wait_for_crtc_hw_done/wait_for_connector_hw_done
- Get drm_device using an intel_display instead of drm_i915_private ptr.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241025160259.3088727-2-imre.deak@intel.com