[WATCHDOG] Orion: add hardware watchdog support

This patch allows the use of the hardware watchdog in the
Marvell Orion series of ARM SoCs.

Signed-off-by: Sylver Bruneau <sylver.bruneau@googlemail.com>
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>