Bluetooth: hci_ath: Replace mdelay with msleep in ath_wakeup_ar3k

ath_wakeup_ar3k() is never called from atomic context.

It is only called by ath_hci_uart_work() that is only called in
ath_open() via INIT_WORK().
All of the above functions do not enter atomic context along the way.

Despite never getting called from atomic context, ath_wakeup_ar3k() calls
mdelay() for busy wait.
That is not necessary and can be replaced with msleep to avoid busy wait.

This is found by a static analysis tool named DCNS written by myself.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/hci_ath.c

@@ -71,12 +71,12 @@ static int ath_wakeup_ar3k(struct tty_struct *tty)
 	/* Clear RTS first */
 	tty->driver->ops->tiocmget(tty);
 	tty->driver->ops->tiocmset(tty, 0x00, TIOCM_RTS);
-	mdelay(20);
+	msleep(20);
 
 	/* Set RTS, wake up board */
 	tty->driver->ops->tiocmget(tty);
 	tty->driver->ops->tiocmset(tty, TIOCM_RTS, 0x00);
-	mdelay(20);
+	msleep(20);
 
 	status = tty->driver->ops->tiocmget(tty);
 	return status;