drm/i915/sdvo: Filter out invalid outputs more sensibly

We try to filter out the corresponding xxx1 output
if the xxx0 output is not present. But the way that is
being done is pretty awkward. Make it less so.

Cc: stable@vger.kernel.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221026101134.20865-2-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit cc1e6639)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>