ARM: dts: rcar-gen2: Add interrupt properties to watchdog nodes

Driver doesn't use it yet, but let's describe the HW properly.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20220322095512.4707-2-wsa+renesas@sang-engineering.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>