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

The advantage is that these specifiers are machine-parseable which helps
license conformance, e.g. for packaging barebox in Debian.

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

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Roland Hieber <rhi@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

The CREDITS file was removed from barebox in 2015 by commit 6570288f2d97
("Remove the CREDITS file"). Remove references to it from several files.

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

The TX6 boards come with 3 different PMIC variants from which we
currently only support the ltc3673. Detect the other two by i2c
address and set them up correctly. The code is based on the karo
U-Boot port.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>