MAINTAINERS: update the audit entry

Bring the audit subsystem entry up to date with the following changes:

* Add our patchwork link.  I'm not sure this is of much use for
anyone but the maintainer, but there is a provision for including it
here so we might as well include it.

* Add a bug report URI.  I suspect most everyone knows to send mail
to the mailing list if they hit a bug, but let's make it official.

* Add a link to the audit tree process/management documentation.
While the doc exists both in the canonical kernel.org location and the
GitHub mirror, provide a link to the mirror as GitHub does a better
job rendering the Markdown.

* Update the source tree's git URI to use https.

* Aside from changes to the audit code itself, we also would like to
be notified when the audit call sites are changed so we are adding an
audit_XXX(...) regex to try and catch all of the callers.

Signed-off-by: Paul Moore <paul@paul-moore.com>