drm/i915/sdvo: Nuke the duplicate sdvo->port

We already have encoder->port so get rid of the duplicate
sdvo->port.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230825134431.24391-4-ville.syrjala@linux.intel.com