tty: serial: omap: fix Sparse warnings

Fix the following Sparse warnings:

drivers/tty/serial/omap-serial.c:1418:49: warning: incorrect \
	type in argument 2 (different address spaces)
drivers/tty/serial/omap-serial.c:1418:49:    expected void const \
	[noderef] <asn:1>*from
drivers/tty/serial/omap-serial.c:1418:49:    got struct serial_rs485 \
	*<noident>
drivers/tty/serial/omap-serial.c:1426:35: warning: incorrect \
	type in argument 1 (different address spaces)
drivers/tty/serial/omap-serial.c:1426:35:    expected void [noderef] \
	<asn:1>*to
drivers/tty/serial/omap-serial.c:1426:35:    got struct serial_rs485 \
	*<noident>

Reported-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/omap-serial.c

@@ -1398,15 +1398,15 @@ serial_omap_ioctl(struct uart_port *port, unsigned int cmd, unsigned long arg)
 
 	switch (cmd) {
 	case TIOCSRS485:
-		if (copy_from_user(&rs485conf, (struct serial_rs485 *) arg,
+		if (copy_from_user(&rs485conf, (void __user *) arg,
 					sizeof(rs485conf)))
 			return -EFAULT;
 
 		serial_omap_config_rs485(port, &rs485conf);
 		break;
 
 	case TIOCGRS485:
-		if (copy_to_user((struct serial_rs485 *) arg,
+		if (copy_to_user((void __user *) arg,
 					&(to_uart_omap_port(port)->rs485),
 					sizeof(rs485conf)))
 			return -EFAULT;