net: bridge: multicast: add EHT host filter_mode handling

We should be able to handle host filter mode changing. For exclude mode
we must create a zero-src entry so the group will be kept even without
any S,G entries (non-zero source sets). That entry doesn't count to the
entry limit and can always be created, its timer is refreshed on new
exclude reports and if we change the host filter mode to include then it
gets removed and we rely only on the non-zero source sets.

Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>