[WATCHDOG] s3c2410_wdt - initialize watchdog irq resource

In the error path of s3c2410wdt_probe() and in s3c2410wdt_remove(),
we're using wdt_irq without initialising it, leading to a oops.

Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>