net: rtnl: introduce rcu_replace_pointer_rtnl

Introduce the rcu_replace_pointer_rtnl helper to lockdep check rtnl lock
rcu replacements, alongside the already existing helpers.

This is a quality of life helper so instead of using:
   rcu_replace_pointer(rp, p, lockdep_rtnl_is_held())
   .. or the open coded..
   rtnl_dereference() / rcu_assign_pointer()
   .. or the lazy check version ..
   rcu_replace_pointer(rp, p, 1)
Use:
   rcu_replace_pointer_rtnl(rp, p)

Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>