Makefile: add missing license header

This file was created in 2016, but proper header was not added at the
time. Adding it now to prevent future pre-upload script complaints.

BRANCH=cr50, cr50-mp
BUG=none
TEST=no more pre-upload warnings generated by repo

Change-Id: I3293fab86ddeb1d2e2ce16e345316800cc3cd88d
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1454181
Reviewed-by: Randall Spangler <rspangler@chromium.org>
1 file changed