coreboot rush: Add support for rush board

Add basic support for rush board

BUG=None
BRANCH=None
TEST=Compiles successfully with soc tegra132 and armv8 arch selected for
romstage and ramstage

Change-Id: Ica57c68d230e4e0e9916729752395843de188733
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://chromium-review.googlesource.com/197399
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
7 files changed