commands/*: Replace license and copyright boilerplate by SPDX identfiers ...

While at it also drop references to the non-existing CREDITS file and do
some small rearrangements for some uniform formatting.
(SPDX-License-Identifier first, then copyright texts and then an empty
line.)

The advantage is that these specifiers are machine-parseable which helps
license conformance.

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

commands: drvinfo: Make locally used function static ...

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

drvlist: factor the driver list out of 'devinfo' ...

The command 'devinfo' was first spitting out all devices, and then
also all drivers. This patch separates them into two commands,
'devinfo' as before, and also the new command 'drvinfo'

Signed-off-by: Holger Schurig <holgerschurig@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>