sfc: fixes to filter restore handling

If the NIC is switched from full-featured to low-latency, encapsulated
 filters are no longer available, and this causes errors. This patch
 removes those filters from the filter table on restore.
Also, if filters which are removed by the above, or which we fail to
 insert when restoring filters, were UC, MC or broadcast default
 filters, invalidate the corresponding vlan->default_filters entry.

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