watchdog: f71808e_wdt: add F71862FG, F71869 to Kconfig

Update Kconfig with the additional Fintek hardware that we support.

Signed-off-by: Lutz Ballaschke <vegan.grindcore@googlemail.com>
Acked-by: Giel van Schijndel <me@mortis.eu>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>