arm64: dts: imx8dxl: Pass fsl,imx8dxl-sc-wdt

Pass 'fsl,imx8dxl-sc-wdt' to fix the following schema warning:

system-controller: watchdog:compatible:0: 'fsl,imx8qxp-sc-wdt' was expected
	from schema $id: http://devicetree.org/schemas/firmware/fsl,scu.yaml#
system-controller: watchdog:compatible: ['fsl,imx-sc-wdt'] is too short
	from schema $id: http://devicetree.org/schemas/firmware/fsl,scu.yaml#



Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>