arm64: dts: imx8mq-evk: add missing MDIO / PHY nodes

Populate the fec1 node with the missing MDIO and PHY entries.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>