docs: mips: add to the documentation body as ReST

Manually convert the AU1xxx_IDE.README file to ReST and add
to a MIPS book as part of the main documentation body.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Paul Burton <paul.burton@mips.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>