drm/i915/sdvo: Issue SetTargetOutput prior to GetAttachedDisplays

drm/i915/sdvo: Issue SetTargetOutput prior to GetAttachedDisplays

I have at least one SDVO device (some Lenovo DVI-I ADD2 card,
based on Conexant CX25904) where GetAttachedDisplays returns
success but fails to report any attached displays unless we
precede the command with a SetTargetOutput. Make it so.

I wasn't able to spot anything in the SDVO spec stating that
this should be necessary, but real world wins over spec.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230705202122.17915-2-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>