watchdog: Zodiac Aerospace RAVE Switch Watchdog Processor Driver

This patch adds a driver for the Zodiac Aerospace RAVE Watchdog Procesor.
This device implements a watchdog timer, accessible over I2C.

Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>