Revert "USB: serial: fix hang when opening port"

This reverts commit eba0e3c3a0ba7b96f01cbe997680f6a4401a0bfc.

When merged together (usb-linus and usb-next), this fix isn't needed and
causes a build error.  Revert the commit to solve the build issue.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/usb-serial.c

@@ -892,7 +892,6 @@ static int usb_serial_probe(struct usb_interface *interface,
 		port->port.ops = &serial_port_ops;
 		port->serial = serial;
 		spin_lock_init(&port->lock);
-		init_waitqueue_head(&port->delta_msr_wait);
 		/* Keep this for private driver use for the moment but
 		   should probably go away */
 		INIT_WORK(&port->work, usb_serial_port_work);