nvram: erase nvram after it is used up

This change makes depthcharge erase nvram if it is used up. To make
erase work, offset and size of nvram have to be 64kb aligned.

BUG=b:23759943
BRANCH=smaug
TEST=crafted a binary with nvram used up. ran reboot bootloader.
verified "nvram is used up..." message and fastboot mode is
entered.

Change-Id: Ide9ae58c367e51ecf917a2285511321319a39ce9
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/297731
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
(cherry picked from commit 444d444e9896d79187b4cf366deaf1706351fc5d)
Reviewed-on: https://chromium-review.googlesource.com/297793
2 files changed