With the introduction of SPDX-License-Identifier headers, we don't need a ton
of header boilerplate in every file. Simplify the files and rely on the top
level for the full licence text.
(Bitbake rev: 695d84397b68cc003186e22f395caa378b06bc75)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>