cros_bundle_firmware: Indicate the amount of space used in each section

Add a 'used' property to every section which indicates how much of the space
is actually used. This can be used by firmware to reduce the amount of data
read.

BUG=chrome-os-partner:21115
TEST=FEATURES=test sudo -E  emerge cros-devutils

Change-Id: Ic995f6c8ea3f67af907dad2b3238986adcb4c460
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/62584
3 files changed