watchdog: bd70528: Initial support for ROHM BD70528 watchdog block

Initial support for watchdog block included in ROHM BD70528
power management IC.

Configurations for low power states are still to be checked.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>