usb-serial: remove NULL check

Julia Lawell found a case where a NULL check was misplaced in the
usb-serial code. However as the object in question cannot be NULL the
check can simply be removed.
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/usb/serial/usb-serial.c

@@ -511,9 +511,6 @@ static void usb_serial_port_work(struct work_struct *work)
 
 	dbg("%s - port %d", __func__, port->number);
 
-	if (!port)
-		return;
-
 	tty = tty_port_tty_get(&port->port);
 	if (!tty)
 		return;