Re-licence bootimg.h to BSD-3 am: a306f82e5a am: 5cea0cfc8b

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/3281575

Change-Id: I0c396e3c996aaf79b090e7658fdd59c744ec9e73
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>