This add watchdog driver for broadcom 47xx device.
It uses the ssb subsytem to access embeded watchdog device.

Because the watchdog timeout is very short (about 2s), a soft timer is used
to increase the watchdog period.

Note : A patch for exporting the ssb_watchdog_timer_set will
be submitted on next linux-mips merge. Without this patch it can't 
be build as a module.
Signed-off-by: Aleksandar Radovanovic <biblbroks@sezampro.rs>
Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
Tested-by: Florian Fainelli <florian@openwrt.org>
Cc: Ralf Baechle <ralf@linux-mips.org>                                                                                       
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>