docs-rst: sphinxify 802.11 documentation

This is just a very basic conversion, I've split up the original
multi-book template, and also split up the multi-part mac80211
part in the original book; neither of those were handled by the
automatic pandoc conversion.

Fix errors that showed up, resulting in a much nicer rendering,
at least for the interface combinations documentation.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>