cros_bundle_firmware: use  exynos.py in write_firmware.py

The earlier refactor of Exynos BL2 image processing left behind a call
site in write_firmware.

This change fixes the problem.

BUG=chrome-os-partner:18447
TEST=manual
   . cros_write_firmware now succeeds

Change-Id: I4027f3775e3661506c3d8af569ebf711d3d7bc8f
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/58120
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed