Use compressed squashfs for kernel (#1418)

* Add squashfs with LZ4 and LZO compression to Barebox

* Add squashfs with LZO compression to U-Boot

* Use squashfs for Linux kernel partition

Generate a squashfs image with LZO compression for the Linux kernel
partition. Adjust the boot scripts to be file system independent commands
to boot from squashfs.

buildroot-external/scripts/hdd-image.sh

@@ -89,14 +89,7 @@ function create_kernel_image() {
 
     # Make image
     rm -f "${kernel_img}"
-    truncate --size="${KERNEL_SIZE}" "${kernel_img}"
-    mkfs.ext4 -L "hassos-kernel" -E lazy_itable_init=0,lazy_journal_init=0 -O ^64bit "${kernel_img}"
-
-    # Mount / init file structs
-    sudo mkdir -p /mnt/data/
-    sudo mount -o loop "${kernel_img}" /mnt/data
-    sudo cp "${kernel}" /mnt/data/
-    sudo umount /mnt/data
+    mksquashfs "${kernel}" "${kernel_img}" -comp lzo
 }