Get size using --get-size in flashrom_util.py instead of reading whole flash.

Also restore to BIOS after running firmware_RomSize test.

TEST=run firmware_RomSize test in AGZ and non-Mario.

Change-Id: I876842b9670cc0c2294781e859e239a90598d33e

Review URL: http://codereview.chromium.org/3296001
2 files changed