stable-kernel-rules.rst: add link to networking patch queue
The networking maintainer keeps a public list of the patches being
queued up for the next round of stable releases. Be sure to check there
before asking for a patch to be applied so that you do not waste
people's time.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jonathan Corbet <corbet@lwn.net>