mvebu: add sysupgrade support for clearfog

Add and enable sysupgrade support for clearfog boards, based on how the
brcm2708 target does it.

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Acked-by: Felix Fietkau <nbd@nbd.name>

target/linux/mvebu/base-files/lib/upgrade/clearfog.sh

@@ -0,0 +1,32 @@
+get_magic_at() {
+	local file="$1"
+	local pos="$2"
+	get_image "$file" | dd bs=1 count=2 skip="$pos" 2>/dev/null | hexdump -v -n 2 -e '1/1 "%02x"'
+}
+
+platform_check_image_clearfog() {
+	local file="$1"
+	local magic
+
+	magic=$(get_magic_at "$file" 510)
+	[ "$magic" != "55aa" ] && {
+		echo "Failed to verify MBR boot signature."
+		return 1
+	}
+
+	return 0;
+}
+
+platform_do_upgrade_clearfog() {
+	sync
+	get_image "$1" | dd of=/dev/mmcblk0 bs=2M conv=fsync
+	sleep 1
+}
+
+platform_copy_config_clearfog() {
+	mkdir -p /boot
+	[ -f /boot/kernel.img ] || mount -t vfat -o rw,noatime /dev/mmcblk0p1 /boot
+	cp -af "$CONF_TAR" /boot/
+	sync
+	umount /boot
+}