net: introduce netif_addr_lock_nested() and call if when appropriate

dev_uc_sync() and dev_mc_sync() are acquiring netif_addr_lock for
destination device of synchronization. Since netif_addr_lock is
already held at the time for source device, this triggers lockdep
deadlock warning.

There's no way this deadlock can happen so use spin_lock_nested() to
silence the warning.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>