drm/i915/dp: Write the source OUI during connector detection

The DP sink's capabilities, like DSC, may depend on the source OUI
written to the sink. On eDP this OUI value could have been reset before
the detection started if the panel power on it got disabled. Make sure
the OUI is re-written at the beginning of detection in this case, before
the sink capabilities are read out.

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/20241025160259.3088727-8-imre.deak@intel.com