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 <[e-mail]>
Acked-by: David S. Miller <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/process/stable-kernel-rules.rst

···
  - If the patch covers files in net/ or drivers/net please follow netdev stable
    submission guidelines as described in
    :ref:`Documentation/networking/netdev-FAQ.rst <netdev-FAQ>`
+   after first checking the stable networking queue at
+   https://patchwork.ozlabs.org/bundle/davem/stable/?series=&submitter=&state=*&q=&archive=
+   to ensure the requested patch is not already queued up.
  - Security patches should not be handled (solely) by the -stable review
    process but should follow the procedures in
    :ref:`Documentation/admin-guide/security-bugs.rst <securitybugs>`.