[U-Boot] [PATCH v3 0/2] rockchip: make_fit_atf.py Eliminate pyelftools dependency

[Chris Webb <chris@arachsys.com>]

Building for rockchip, make_fit_atf.py depends on pyelftools, a non-bundled
python module that is not used elsewhere in building u-boot or the kernel.

We only use pyelftools to pull out PT_LOAD segments. ELF is very simple, so
doing this manually is easy and spares users the extra dependency. In fact,
a straightforward implementation shrinks make_fit_aft.py rather than adding
complexity.

Andy Yan's patch

  https://gitlab.denx.de/u-boot/custodians/u-boot-rockchip/commit/619f002db864ef8caa30863bde62df5c651a7312

is a prerequisite for this. The new code does not erroneously count
GNU_STACK sections and therefore without the above patch, the loadables in
the conf section will always be one short, even where GNU_STACK is present.

I have tested this script with python 2 and 3 against all bl31 elf files at

  https://github.com/rockchip-linux/rkbin/tree/master/bin/rk33

as well as an rk3399 bl31.elf built locally from the master branch of

  https://github.com/ARM-software/arm-trusted-firmware

to which my toolchain added the extra GNU_STACK segment.

In each case, identical *.bin files were produced compared to the pyelftools
implementation, and a correct .its configuration (without off-by-one error)
was emitted, with and without dtbs supplied to the script.

Changes in v2:
  - no exception on a valid but completely empty bl31 ELF file
  - restrict documentation updates to the Rockchip docs (!)

Changes in v3:
  - code style: add correct whitespace around multiply operator