docs: conf.py: adjust the LaTeX document output

docs: conf.py: adjust the LaTeX document output

Changeset f546ff0c0c07 ("Move our minimum Sphinx version to 1.7")
cleaned up some compatibility issues with previous Sphinx
versions, but it also dropped the PDF margin sets.

Without that, the media documentation won't build fine, as
the margins are too wide to display texts with monospaced
fonts.

While here, align the  "latex_elements = {" values, and add
a few other sphinxsetup configs in order to allow Sphinx to
wrap long lines on literal blocks.

Fixes: f546ff0c0c07 ("Move our minimum Sphinx version to 1.7")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
 Documentation/conf.py | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)
Link: https://lore.kernel.org/r/911fbac185dd09c7df715cf4153361b81f04b7ad.1614787053.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>