[WATCHDOG] Add support for the WM8350 watchdog

This driver implements support for the watchdog functionality provided
by the Wolfson Microelectronics WM8350, a multi-function audio and
power management subsystem intended for use in embedded systems. It is
based on a driver originally written by Graeme Gregory, though it has
been extensively modified since then.

Use of a GPIO to kick the watchdog is not yet supported.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>