drm/i915: fix a possible refcount leak in intel_dp_add_mst_connector()

If drm_connector_init fails, intel_connector_free will be called to take
care of proper free. So it is necessary to drop the refcount of port
before intel_connector_free.

Fixes: 091a4f9194 ("drm/i915: Handle drm-layer errors in intel_dp_add_mst_connector")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220624130406.17996-1-jose.souza@intel.com
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>

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

@@ -839,6 +839,7 @@ static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topolo
 	ret = drm_connector_init(dev, connector, &intel_dp_mst_connector_funcs,
 				 DRM_MODE_CONNECTOR_DisplayPort);
 	if (ret) {
+		drm_dp_mst_put_port_malloc(port);
 		intel_connector_free(intel_connector);
 		return NULL;
 	}