ARM: dts: rockchip: add new watchdog compatible to rk322x.dtsi

ARM: dts: rockchip: add new watchdog compatible to rk322x.dtsi

The watchdog compatible strings are suppose to be SoC orientated.
In the more recently added Rockchip rk322x.dtsi file only
the fallback string "snps,dw-wdt" is used, so add the new
compatible string:

"rockchip,rk3228-wdt", "snps,dw-wdt"

make ARCH=arm dtbs_check
DT_SCHEMA_FILES=Documentation/devicetree/bindings/watchdog/snps,dw-wdt.yaml

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20201218120534.13788-3-jbx6244@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>