arm64: dts: imx8qm-apalis: Remove invalid FEC property

The 'fsl,rgmii_txc_dly' is not a valid property.

Remove it to fix the following schema warning:

imx8qm-apalis-ixora-v1.1.dtb: ethernet@5b040000: Unevaluated properties are not allowed ('fsl,rgmii_txc_dly' was unexpected)
	from schema $id: http://devicetree.org/schemas/net/fsl,fec.yaml#



Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>