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.comAcked-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_sdvo.c

@@ -2135,6 +2135,10 @@ intel_sdvo_detect(struct drm_connector *connector, bool force)
 	if (!INTEL_DISPLAY_ENABLED(i915))
 		return connector_status_disconnected;
 
+	if (!intel_sdvo_set_target_output(intel_sdvo,
+					  intel_sdvo_connector->output_flag))
+		return connector_status_unknown;
+
 	if (!intel_sdvo_get_value(intel_sdvo,
 				  SDVO_CMD_GET_ATTACHED_DISPLAYS,
 				  &response, 2))