layerscape: Add ls1028ardb support

layerscape: Add ls1028ardb support

Add support for NXP LS1028ARDB reference board. It's a dual core
Coretex-A53 board with 4G RAM and 5 Eternet ports (4 ports are
connected to MSCC Felix switch).

The original layout of NXP board has been kept but firmware
images are adapted to be more sysupgrade friendly. At the moment
NOR and SD boots are supported.

NOR flash instructions:
* make sd card with sdboot image
* boot
* write firmware image to spi flash
$ mtd write /tmp/openwrt-layerscape-armv8_64b-fsl_ls1028a-rdb-
squashfs-firmware.bin /dev/mtd0
* change jumper to NOR boot and reset

V3:
 * Added board specific network defaults for lan/wan

v2:
 * Added INA220 curent monitor, PCF2129 RTC clock and NXP
   SA56004ED temperature sensor to default packages
 * removed compat fixups for thist board

Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@protonmail.ch>