crossystem: Move mosys based VbNv functions to shared code

The code to read/write vbnv with mosys was implemented in the
ARM specific code so move it to the generic crosystem code
so it can be used on x86.

No functional changes in this commit.

BUG=chrome-os-partner:51846
BRANCH=none
TEST=emerge-chell vboot_reference; emerge-oak vboot_reference

Change-Id: I3fe18fadb924094e710427208976328caf12a009
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/336310
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
3 files changed