Update pack_firmware to check for overlap
Update pack_firmware to check for overlap

BUG=chromium-os:17187
TEST=change fdt to have overlaps and gaps, then cros_bundle_firmware -w
Manual check that these are found

Change-Id: If387622929a7d42a10c2a71f3622d490cec770dc
Reviewed-on: http://gerrit.chromium.org/gerrit/4115
Reviewed-by: Che-Liang Chiou <57969107b634cf11cb64e9d768fd46929066adab@chromium.org>
Tested-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>

coreos/dev-util,marineam/coreos-dev-util,mgireesh05/dev-util,coreos/dev-util,coreos/dev-util,mgireesh05/dev-util,marineam/coreos-dev-util,mgireesh05/dev-util