watchdog: s3c2410_wdt - Fix on handling of the request_mem_region fail

If the request for wdt_mem region fails, this patch modifies the driver
such that, it does not try to release the wdt_mem region on exit.

Signed-off-by: Banajit Goswami <banajit.g@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>