Merge branch 'bridge-PIM-hello'

Nikolay Aleksandrov says:

====================
bridge: add support for PIM hello router ports

The first 3 patches of this set do minor cleanups and add some helpers to
the PIM header file. Patch 4 adds a way to detect mcast router ports via
PIM hello messages, they're marked as temporary and are not considered for
querier. There's more detailed information in patch 4's commit message.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>