Instead of people open coding the offset field access within a
struct buffer provide buffer_offset() so that the implementation
can change if needed without high touch in the code base.
Change-Id: I751c7145687a8529ab549d87e412b7f2d1fb90ed
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13468
Tested-by: build bot (Jenkins)
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>