Add a second list for unicast filters and generalize the
efx_ptp_insert/remove_filters functions to allow acting in any of the 2
lists.

No filters for unicast are inserted yet. That will be done in the next
patch.

The reason to use 2 different lists instead of a single one is that, in
next patches, we will want to check if unicast filters are already added
and if they're expired. We don't need that for multicast filters.
Reported-by: Yalin Li <yalli@redhat.com>
Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Reviewed-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>