ARM: at91/dt: add watchdog properties to kizbox board

Add watchdog specific config for kizbox board.

Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>