arm64: dts: freescale: imx93-phycore-som: Move ethernet0 alias to SoM

arm64: dts: freescale: imx93-phycore-som: Move ethernet0 alias to SoM

Move alias for ethernet0 interface to the phyCORE-i.MX93 SoM include
file. The reason behind it is that the physical location of the PHY chip
connected to FEC interface is on the SoM itself and alias thus belongs
into the SoM device-tree. Consequently, it can be used by all boards
based on the phyCORE-i.MX93 SoM (phyBOARD-Segin and phyBOARD-Nash).

This also enables us to mark FEC interface as the primary / first for
networking in the bootloader and systemd (predictable interface names).

Signed-off-by: Primoz Fiser <primoz.fiser@norik.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>