The WM831x series of devices provide a watchdog with configurable
behaviour on timer expiry.

Currently this driver support refreshes via a register or GPIO line and
autonomous refreshes from a hardware source (eg, a clock).
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>