tegra124: Add a custom bootblock implementation.

This implementation is the same as the general one except that it removes all
the things that don't work on an ARMv4.

TEST=Built for Nyan. With this and other changes, built and booted on Nyan and
verified that it was getting into the bootblock.

Change-Id: I1108a79cc656b26f7d48df20aef3016cf5ae3182
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/171019
Reviewed-by: Ronald Minnich <rminnich@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
4 files changed