greybus: connection: fix offloaded-connection ping cport id

The host-device cport_ping callback expects the AP side cport id, but
was incorrectly passed the interface cport id.

Note that no host-device driver currently implements this callback, and
that it is soon even to be removed.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/connection.c

@@ -527,7 +527,7 @@ static int gb_connection_ping(struct gb_connection *connection)
 		if (!hd->driver->cport_ping)
 			return 0;
 
-		ret = hd->driver->cport_ping(hd, connection->intf_cport_id);
+		ret = hd->driver->cport_ping(hd, connection->hd_cport_id);
 	} else {
 		ret = gb_connection_ping_operation(connection);
 	}