rtc: ds1374: Remove unused variable

Remove unused variable 'res' and fix the following build warning:

drivers/rtc/rtc-ds1374.c:667:6: warning: unused variable 'res' [-Wunused-variable]

Reported-by: Olof's autobuilder <[e-mail]>
Signed-off-by: Fabio Estevam <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/rtc/rtc-ds1374.c

···
 {
 	struct ds1374 *ds1374 = i2c_get_clientdata(client);
 #ifdef CONFIG_RTC_DRV_DS1374_WDT
-	int res;
-
 	misc_deregister(&ds1374_miscdev);
 	ds1374_miscdev.parent = NULL;
 	unregister_reboot_notifier(&ds1374_wdt_notifier);