ipq806x: enable gpio watchdog support
The kernel driver gpio-wdt or the userspace tool om-watchdog can be used to
trigger external gpio watchdog chips. The gpio-wdt driver has the benefit
that it can be configured together with the rest of the device in the DTS
and better integrates in the OpenWrt via procd.
Signed-off-by: Sven Eckelmann <[email protected]>