watchdog: DA9055 Watchdog driver

This is the Watchdog patch for the DA9055 PMIC. This patch has got dependency on
the DA9055 MFD core.

This patch is functionally tested on SMDK6410

Signed-off-by: David Dajun Chen <dchen@diasemi.com>
Signed-off-by: Ashish Jangam <ashish.jangam@kpitcummins.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>