vboot: restructure vboot work buffer handling

For the purpose of isolating the work buffer logic
the surface area of the API was slimmed down.  The
vb2_working_data structure is no longer exposed,
and the function signatures are updated accordingly.

TEST=Built and booted glados.

Change-Id: If64184a79e9571ee8ef9822cfce1eda20fceee00
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11818
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
5 files changed