new_variant: add fw_build_config to upload

Add the fw_build_config CL to the upload list for all reference
boards that use fw_build_config.

BUG=b:158602858
TEST=create a new variant of puff, volteer, trembyle, dalboz,
waddledee, or waddledoo. Proceed through the fitimage creation and
coreboot push steps. When new_variant.py uploads the rest of the
CLs, the _FW_BUILD_CONFIG CL will be part of that upload.

Change-Id: I4e9f967a564819bcc460612746c2d931999b117e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2254299
Tested-by: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Paul Fagerburg <pfagerburg@chromium.org>
4 files changed