arm64: dts: imx8qxp-mek: Remove unexisting Ethernet PHY

There is only on Ethernet port and one Ethernet PHY on imx8qxp-mek.

Remove the unexisting ethphy1 port.

This fixes a run-time warning:

mdio_bus 5b040000.ethernet-1: MDIO device at address 1 is missing.

Fixes: fdea904e ("arm64: dts: imx: add imx8qxp mek support")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>