docs: net: convert two README files to ReST format

There are two README files there with doesn't have a .txt
extension nor are at ReST format.

In order to help with the docs conversion to ReST, rename those
and manually convert them to ReST format.

As there are lot more to be done for networking to be part of
the documentation body, for now mark those two files with
:orphan:, in order to supress a build warning.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>