If hw does not support vlans, dont call nv_vlan_mode because it has no point.
I believe that this should fix issues on older non-vlan supportive
chips (like Ingo has).

Reported-ty: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>