drm/i915/dp: Write the source OUI for eDP before detecting sink capabilities

The eDP sink's capabilities, like DSC, may depend on the source OUI
written to the sink, so ensure the OUI is written before reading out the
capabilities.

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/20241025160259.3088727-7-imre.deak@intel.com