docs: add some new files to their respective index.rst files

There were some new file additions for Kernel 5.7 and 5.8
that weren't added at the corresponding index file.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/9fd4d04f0d122ff38b5342a0098d99cc2f546652.1599660067.git.mchehab+huawei@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>