CHERRY-PICK: daisy: add vbnvcontext read/write command

These commands let you read/write VbNvContext from/to EC's nvram.

BRANCH=snow
BUG=chrome-os-partner:13766
TEST=build for Snow and Link, and run on Snow

mosys nvram vbnvcontext write 0123456789abcdef0123456789ABCDEF
mosys -l nvram vbnvcontext read
vbnvcontext          | 0123456789abcdef0123456789abcdef

mosys nvram vbnvcontext write 00000000000000000000000000000000
mosys -l nvram vbnvcontext read
vbnvcontext          | 00000000000000000000000000000000

Change-Id: I6748c3efe84334d7036e4472e40e3c222c46d61c
Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/32825
Reviewed-on: https://gerrit.chromium.org/gerrit/37272
Reviewed-by: Katie Roberts-Hoffman <katierh@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>
7 files changed