mvebu: cortexa53: uDPU/eDPU convert to dual firmware (A/B)

mvebu: cortexa53: uDPU/eDPU convert to dual firmware (A/B)

Methode uDPU and eDPU devices are one of the rare ones with a completely
custom image format being used with custom partition table with F2FS.

Instead of converting the boards to dual firmware (A/B style) and further
expand the already convoluted custom scripts, especially considering that
dual firmware conversion is a breaking change anyway, lets convert to using
the generic eMMC sysupgrade based images.

F2FS ZSTD compression is preserved thanks to fstools now supporting its use
on overlays.

Dual firmware support is implemented via U-Boot scripts so no U-Boot
upgrade is required.

Since there is a partition table layout change, eMMC must be wiped and
reflashed with the generated GPT image from OpenWrt initramfs.

Then on each sysupgrade the firmware slot will be altered.

Instructions:
1. Boot into OpenWrt initramfs
2. Copy openwrt-mvebu-cortexa53-methode_edpu-squashfs-emmc-gpt.img.gz to
the device into /tmp
3. Erase eMMC:
dd if=/dev/zero of=/dev/mmcblk0 bs=1M
4. Extract image
gzip -d /tmp/openwrt-mvebu-cortexa53-methode_edpu-squashfs-emmc-gpt.img.gz
5. Flash image
dd if=/tmp/openwrt-mvebu-cortexa53-methode_edpu-squashfs-emmc-gpt.img of=/dev/mmcblk0
6. Reboot

Signed-off-by: Robert Marko <robert.marko@sartura.hr>