net: bridge: mcast: remove unreachable EHT code

In the initial EHT versions there were common functions which handled
allow/block messages for both INCLUDE and EXCLUDE modes, but later they
were separated. It seems I've left some common code which cannot be
reached because the filter mode is checked before calling the respective
functions, i.e. the host filter is always in EXCLUDE mode when using
__eht_allow_excl() and __eht_block_excl() thus we can drop the host_excl
checks inside and simplify the code a bit.

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