net: bridge: mcast: factor out common allow/block EHT handling

We hande EHT state change for ALLOW messages in INCLUDE mode and for
BLOCK messages in EXCLUDE mode similarly - create the new set entries
with the proper filter mode. We also handle EHT state change for ALLOW
messages in EXCLUDE mode and for BLOCK messages in INCLUDE mode in a
similar way - delete the common entries (current set and new set).
Factor out all the common code as follows:
 - ALLOW/INCLUDE, BLOCK/EXCLUDE: call __eht_create_set_entries()
 - ALLOW/EXCLUDE, BLOCK/INCLUDE: call __eht_del_common_set_entries()

The set entries creation can be reused in __eht_inc_exc() as well.

Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>