cros_bundle_firmware: Tidy up pack_firmware for new dtc
cros_bundle_firmware: Tidy up pack_firmware for new dtc

The new device-tree package requires different parameters. Adjust
pack_firmware to handle this.

Also fix the CmdError bug which this exposed.

BUG=chromium-os:19724
TEST=cros_bundle_firmware -w; see that it succeeds now

Change-Id: I316c724890d6c90006aa45526218fedd654ceac7
Reviewed-on: https://gerrit.chromium.org/gerrit/17766
Commit-Ready: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Tested-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>

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