arm64: dts: freescale: Add GMAC Ethernet for S32G2 EVB and RDB2 and S32G3 RDB3

arm64: dts: freescale: Add GMAC Ethernet for S32G2 EVB and RDB2 and S32G3 RDB3

Add support for the Ethernet connection over GMAC controller connected to
the Micrel KSZ9031 Ethernet RGMII PHY located on the boards.

The mentioned GMAC controller is one of two network controllers
embedded on the NXP Automotive SoCs S32G2 and S32G3.

The supported boards:
 * EVB:  S32G-VNP-EVB with S32G2 SoC
 * RDB2: S32G-VNP-RDB2
 * RDB3: S32G-VNP-RDB3

Tested-by: Enric Balletbo i Serra <eballetb@redhat.com>
Signed-off-by: Jan Petrous (OSS) <jan.petrous@oss.nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>