docs: kernel_include.py: document all supported parameters

docs: kernel_include.py: document all supported parameters

As we're actually a fork of Sphinx Include, update its
docstring to contain the documentation for the actual
implemented parameters.

Let's use :param: for parameters, as defined at:
https://sphinx-rtd-tutorial.readthedocs.io/en/latest/docstrings.html

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/f193160889a2dc296b4df2cc7ebc9934d717ccef.1755872208.git.mchehab+huawei@kernel.org