Obtaining the CBI_TAG_BOARD_VERSION value wasn't in the code base.
Add the binding for it so it can be used.
BUG=b:153640981
Change-Id: Ie2f289631f908014432596448e56b5048a196a10
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40355
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>