cros_bundle_firmware: Add new progress message after GBB
cros_bundle_firmware: Add new progress message after GBB

At present it looks like we take ages to produce the GBB. Add a new
progress message to fix that.

BUG=none
BRANCH=none
TEST=manual
Run cros_bundle_firmware as normal and check that the new messages
appears.

Change-Id: I0fac39d0b41631090076a076d3558d87a0abcbd8
Signed-off-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39875
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

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