cbfstool: Add attributes for position and alignment constraints.

cbfstool: Add attributes for position and alignment constraints.

Add functionality to cbfstool to generate file attributes
for position and alignment constraints. This new feature
can be activated with the -g option and will generate,
once the option has been enabled, additional attributes
for the files where position, xip or alignment was specified.

Change-Id: I3db9bd2c20d26b168bc7f320362ed41be349ae3a
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/12967
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)