[WATCHDOG] MTX-1 Watchdog driver

This patch adds support for the MTX-1 boards watchdog. If not available the
board will reboot every 100 seconds. It uses the Linux watchdog and timer
APIs.

Signed-off-by: Florian Fainelli <florian.fainelli@int-evry.fr>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>