Add coreboot version to id area

Add coreboot version to id area

There was no good way to extract the build version from an image.

This change will be mostly backward compatible: The only assumption
that could break is that the board name string ends directly before
the 3 dwords that represent .id's "header".

Change-Id: I325491a0c42911d9d6ecd59e21ee1b756c987693
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/537
Reviewed-by: Peter Stuge <peter@stuge.se>
Tested-by: build bot (Jenkins)