Use the full compatible list for the imx8dl FEC as per fsl,fec.yaml.

This fixes the following schema warning:

imx8dxl-evk.dtb: ethernet@5b040000: compatible: 'oneOf' conditional failed, one must be fixed:
	['fsl,imx8qm-fec'] is too short
	'fsl,imx8qm-fec' is not one of ['fsl,imx25-fec', 'fsl,imx27-fec', 'fsl,imx28-fec', 'fsl,imx6q-fec', 'fsl,mvf600-fec', 'fsl,s32v234-fec']
	'fsl,imx8qm-fec' is not one of ['fsl,imx53-fec', 'fsl,imx6sl-fec']
	'fsl,imx8qm-fec' is not one of ['fsl,imx35-fec', 'fsl,imx51-fec']
	'fsl,imx8qm-fec' is not one of ['fsl,imx6ul-fec', 'fsl,imx6sx-fec']
	'fsl,imx8qm-fec' is not one of ['fsl,imx7d-fec']
	'fsl,imx8mq-fec' was expected
	'fsl,imx8qm-fec' is not one of ['fsl,imx8mm-fec', 'fsl,imx8mn-fec', 'fsl,imx8mp-fec', 'fsl,imx93-fec']
	'fsl,imx8qm-fec' is not one of ['fsl,imx8dxl-fec', 'fsl,imx8qxp-fec']
	'fsl,imx8qm-fec' is not one of ['fsl,imx8ulp-fec']
	from schema $id: http://devicetree.org/schemas/net/fsl,fec.yaml#Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>