[WATCHDOG] ioremap balanced with iounmap for drivers/char/watchdog/s3c2410_wdt.c

ioremap must be balanced by an iounmap and failing to do so can result
in a memory leak.

Signed-off-by: Amol Lad <amol@verismonetworks.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@osdl.org>