sfc: Move last mc_promisc flag to EF10 filter table state

It is used for EF10 only and logically belongs to EF10 filter table state.
It is OK that it is reset to false on filter table recreation since all
filters are removed on destruction.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>