vboot/make_dev_firmware: extract bitmaps from system firmware instead of prebuilts.
vboot/make_dev_firmware: extract bitmaps from system firmware instead of prebuilts.

make_dev_firmware should trust system firmware blobs instead of using its own
prebuilt binaries.

BUG=chromium-os:12400
TEST=1. make a build with .49+ BIOS, and create the firmware updater
     2. install the new BIOS, turn on developer switch and reboot
     3. an ugly "DEV" screen (in .49) is shown on screen
     4. run the new make_dev_firmware.sh
     5. reboot. seeing the ugly DEV instead of the prebuilt blue screen
     (verified successfully)

Change-Id: If75d2821170649fa869db6a82d879b697f7588e6

Review URL: http://codereview.chromium.org/6614006

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