docs: andes-ae350.md: fix watchdog nodename in dts example

The example should use watchdog as nodename instead of wdt.
This is defined in watchdog common schemas:
https://github.com/torvalds/linux/blob/v6.0/Documentation/devicetree/bindings/watchdog/watchdog.yaml#L19



Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Anup Patel <anup@brainfault.org>