docs: process/4.Coding.rst: Fix a couple of document refs

In Documentation/process/4.Coding.rst there were a couple of paragraphs
that spilled over the 80 character line length. This was likely caused
when the document was converted to reStructuredText. Re-flow the
paragraphs and make the document references proper reStructuredText
:ref: links.

This also adds the appropriate reStructuredText file heading to
kernel-parameters.rst as referenced by the kernel-parameters link in
this patch.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>