[WATCHDOG] NS pc87413-wdt Watchdog driver

New watchdog driver for the NS pc87413-wdt Watchdog Timer.
 
Signed-off-by: Sven Anders <anders@anduras.de>
Signed-off-by: Marcus Junker <junker@anduras.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>