Hide packaged firmware AU signing behind a flag for now.
Hide packaged firmware AU signing behind a flag for now.

The exact firmware packaging is still very much in flux, not to mention current images don't have the firmware autoupdate package.

BUG=none
TEST=none

Change-Id: Idc60c2c9a8fbc83e0c786b4d4f96f371cdb4a49f

Review URL: http://codereview.chromium.org/3151027

geekboxzone/mmallow_external_vboot_reference,ccaapton/vboot_reference,geekboxzone/mmallow_external_vboot_reference,acorn-marvell/vboot_reference,coreboot/vboot,acorn-marvell/vboot_reference,coreboot/vboot,geekboxzone/mmallow_external_vboot_reference,marineam/seismograph,ionave/seismograph,marineam/seismograph,coreboot/vboot,acorn-marvell/vboot_reference,ccaapton/vboot_reference,ionave/seismograph,marineam/seismograph,marineam/seismograph,ccaapton/vboot_reference,geekboxzone/mmallow_external_vboot_reference,coreboot/vboot,coreboot/vboot,geekboxzone/mmallow_external_vboot_reference,acorn-marvell/vboot_reference,ionave/seismograph,ccaapton/vboot_reference