feat(scripts/liminix): make it easy to extract the firmware part of the Zyxel NWA FIT image

This is useful when reflashing the system from scratch in the levitation
mode.

Note that doing this will reset the UBI counter to zero, this is bad for
wear leveling.

Signed-off-by: Ryan Lahfa <ryan@dgnum.eu>

scripts/extract-firmware-from-zyxel-nwa-fit.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p ubootTools
+
+usage() {
+	echo "extract the firmware part to write it manually from a Zyxel NWA FIT image"
+	echo "$0 <zyxel_nwa_fit_image_path> <firmware_output_file>"
+}
+
+ZYXEL_NWA_FIT="$1"
+FIRMWARE_OUTPUT="$2"
+
+dumpimage -T flat_dt -p 0 $ZYXEL_NWA_FIT -o $FIRMWARE_OUTPUT