serial_cs: drop spurious flush_scheduled_work() call

serial_cs doesn't use the system workqueue.  Drop spurious
flush_scheduled_work() call.

This is to prepare for the deprecation and removal of
flush_scheduled_work().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

drivers/serial/serial_cs.c

@@ -330,11 +330,6 @@ static void serial_detach(struct pcmcia_device *link)
 
 	dev_dbg(&link->dev, "serial_detach\n");
 
-	/*
-	 * Ensure any outstanding scheduled tasks are completed.
-	 */
-	flush_scheduled_work();
-
 	/*
 	 * Ensure that the ports have been released.
 	 */