docs: sphinx-build-wrapper: allow -v override -q

docs: sphinx-build-wrapper: allow -v override -q

Documentation builds were using "-q" for a long time, but sometimes
it is nice to see the Sphinx progress, without increasing build
verbosity - which would also turn on kernel-doc verbosity.

Instead of doing that, let's parse the sphinx-build already-existing
-v: each time it is used, it increases the verbosity level.

With that, if the default is to use -q, a single -v will disable
quiet mode. Passing more -v will keep increasing its verbosity.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <38b24e97a3cbd2def418359a8e69b1b087a945ad.1769500383.git.mchehab+huawei@kernel.org>