watchdog: f71808e_wdt: Add Fintek F71869 watchdog

Add Fintek f71869 as a supported watchdog device.

Signed-off-by: Michel Arboi <michel@arboi.fr.eu.org>
Acked-by: Giel van Schijndel <me@mortis.eu>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>