[SERIAL] 8250_early.c passing 0 instead of NULL

Fix sparse warning about passing `0` to  simple_strtoul()
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/serial/8250_early.c

@@ -164,7 +164,7 @@ static int __init parse_options(struct early_uart_device *device, char *options)
 
 	if ((options = strchr(options, ','))) {
 		options++;
-		device->baud = simple_strtoul(options, 0, 0);
+		device->baud = simple_strtoul(options, NULL, 0);
 		length = min(strcspn(options, " "), sizeof(device->options));
 		strncpy(device->options, options, length);
 	} else {