Merge branch 'bridge-mcast-preparations-for-evpn-extensions'

Ido Schimmel says:

====================
bridge: mcast: Preparations for EVPN extensions

This patchset was split from [1] and includes non-functional changes
aimed at making it easier to add additional netlink attributes later on.
Future extensions are available here [2].

The idea behind these patches is to create an MDB configuration
structure into which netlink messages are parsed into. The structure is
then passed in the entry creation / deletion call chain instead of
passing the netlink attributes themselves. The same pattern is used by
other rtnetlink objects such as routes and nexthops.

I initially tried to extend the current code, but it proved to be too
difficult, which is why I decided to refactor it to the extensible and
familiar pattern used by other rtnetlink objects.

Tested using existing selftests and using a new selftest that will be
submitted together with the planned extensions.

[1] https://lore.kernel.org/netdev/20221018120420.561846-1-idosch@nvidia.com/
[2] https://github.com/idosch/linux/commits/submit/mdb_v1
====================

Link: https://lore.kernel.org/r/20221206105809.363767-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>