sfc: Fix VLAN filtering feature if vPort has VLAN_RESTRICT flag

If vPort has VLAN_RESTRICT flag, VLAN tagged traffic will not be
delivered without corresponding Rx filters which may be proxied to and
moderated by hypervisor.

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