bridge: mcast: Propagate MDB configuration structure further

As an intermediate step towards only using the new MDB configuration
structure, pass it further in the control path instead of passing
individual attributes.

No functional changes intended.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>