drm/i915/dp: Populate connector->ddc

drm/i915/dp: Populate connector->ddc

Populate connector->ddc, and thus create the "ddc" symlink
in sysfs for analog DP SST connectors.

Let's also reorder intel_dp_aux_init() vs. drm_connector_init_with_ddc()
a bit to make sure the i2c aux ch is at least somewhat populated
before we pass it on, though drm_connector_init_with_ddc() does
not actually do anything with it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230829113920.13713-8-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>