watchdog: meson: Add meson8b SoC specific data

Add SoC specific data in the watchdog driver for the meson8b SoC.

Signed-off-by: Carlo Caione <carlo@endlessm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>