vboot: rename USB_BOOT_ON_DEV to BOOT_EXTERNAL_ON_DEV

BRANCH=none
BUG=none
TEST=make runtests
TEST=emerge-puff depthcharge

Cq-Depend: chromium:2241263
Change-Id: I4ebfadda3a41c09662f241f04c251784716784e3
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2241418
Reviewed-by: Joel Kitching <kitching@chromium.org>
4 files changed