This adapts all files that were identifed by licensecheck
(https://salsa.debian.org/build-common-team/licensecheck.git) as
licensed under the GPL.

The copyright situation isn't trivially clear for these files, so I didn't
replace the copyright statement here with machine-parseable tags.

While touching these files also do some minor comment reformatting to
get some uniform layout.

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>