watchdog: wdt285: Fix variable type

Variable "new_margin" is checked in the function watchdog_ioctl()
to be non-negative, so change its type to "int".

Signed-off-by: Alexander Shiyan <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/wdt285.c

···
 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 			   unsigned long arg)
 {
-	unsigned int new_margin;
 	int __user *int_arg = (int __user *)arg;
-	int ret = -ENOTTY;
+	int new_margin, ret = -ENOTTY;
 
 	switch (cmd) {
 	case WDIOC_GETSUPPORT: