mvebu: add initial support for Globalscale ESPRESSObin-Ultra

mvebu: add initial support for Globalscale ESPRESSObin-Ultra

This patch adds support for Globalscale ESPRESSObin-Ultra. Device uses
the same Armada-3720 SoC with extended hardware support.

- SoC: Armada-3720
- RAM: 1 GB DDR4
- Flash: 4MB SPI NOR (mx25u3235f) + 8 GB eMMC
- Ethernet: Topaz 6341 88e6341 (4x GB LAN + 1x WAN with 30W PoE)
- WiFI: 2x2 802.11ac Wi-Fi marvell (88w8997 PCIe+USB)
- 1x USB 2.0 port
- 1x USB 3.0 port
- 1x microSD slot
- 1x mini-PCIe slot (USB [with nano-sim slot])
- 1x mini-USB debug UART
- 1x RTC Clock and battery
- 1x reset button
- 1x power button
- 4x LED (RGBY)
- Optional 1x M.2 2280 slot

** Installation **

Copy dtb from build_dir to bin/ and run tftpserver there:
$ cp ./build_dir/target-aarch64_cortex-a53_musl/linux-mvebu_cortexa53/
linux-5.4.65/arch/arm64/boot/dts/marvell/armada-3720-espressobin-ultra.dtb
bin/targets/mvebu/cortexa53/
$ in.tftpd -L -s bin/targets/mvebu/cortexa53/

Connect to the device UART via microUSB port on the back side and power on the device.

Power on the device and hit any key to stop the autoboot.

Set serverip (host IP) and ipaddr (any free IP address on the same subnet), e.g:
$ setenv serverip 192.168.1.10 # Host
$ setenv ipaddr 192.168.1.15 # Device

Ping server to confirm network is working:
$ ping $serverip
Using neta@30000 device
host 192.168.1.15 is alive

Tftpboot the firmware:
$ tftpboot $kernel_addr_r openwrt-mvebu-cortexa53-globalscale_espressobin-ultra-initramfs-kernel.bin
$ tftpboot $fdt_addr_r armada-3720-espressobin-ultra.dtb

Set the console and boot the image:
$ setenv bootargs $console
$ booti $kernel_addr_r - $fdt_addr_r

Once the initramfs is booted, transfer openwrt-mvebu-cortexa53-globalscale_espressobin-ultra-squashfs-sdcard.img.gz
to /tmp dir on the device.

Gunzip and dd the image:
$ gunzip /tmp/openwrt-mvebu-cortexa53-globalscale_espressobin-ultra-squashfs-sdcard.img.gz
$ dd if=/tmp/openwrt-mvebu-cortexa53-globalscale_espressobin-ultra-squashfs-sdcard.img of=/dev/mmcblk0 && sync

Reboot the device.

Signed-off-by: Vladimir Vid <vladimir.vid@sartura.hr>