It's working, but there is quite a few thing that should be fixed or
just to make it better in general. See this initial commit as a working
start, but slighly experimental. I think this will be easier to deal
with in the future when Linaro builds will include more of this by
default.

List of things that could be better or should be fixed.

- It builds a complete *.deb package for Linux kernel, modules, dtb etc,
  that is convenient, but also takes a lot of time and also it seems
  like it always start by cleaning the builds, which is a little bit
  annoying.

- Each time you launch a new kernel build it will generate completely
  new *.deb files, but with incremented version number. Due to this
  we're using linux-image-*.deb when copy files to the device.

- The UART will probably be hardcoded to UART3 after UEFI, since we're
  using a pre-built boot image.

- We build EDK2 even though we download a pre-build boot image. If we
  sort out which kernel, initrd, dtb etc to put into grub, then we will
  probably not need to download a pre-built boot image and would not
  have the issue with the UART.

- The versioning for the OP-TEE debian package is hardcoded in the
  makefile. It would be good to grab that from git instead for example,
  similar to how we do with the autogenerated h-file.

- This is old, but I've noticed that we only support the 4G version (the
  partition table)

- The URLs to the boot-image and the root fs are hardcoded, eventually
  they will become old an invalid at a point in time.

- There are probably quite a few flags that either doesn't work or
  doesn't make sense when having HiKey / Debian as a target.

Signed-off-by: Joakim Bech <joakim.bech@linaro.org>
Tested-by: Joakim Bech <joakim.bech@linaro.org> (HiKey 4G)
Reviewed-by: Pascal Brand <pascal.brand@linaro.org>