There are multiple cases in the documentation where literal blocks are
used for literal, preformatted text. Although it is possible to use
`.. code-block: none` in these cases instead of literal `::` blocks,
follow the principle of least surprise and don't apply any syntax
highlighting at all for literal blocks.

Signed-off-by: Roland Hieber <r.hieber@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>