qed*: Disallow dcbx configuration for VF interfaces.

Dcbx configuration is not supported for VF interfaces. Hence don't populate
the callbacks for VFs and also fail the dcbx-query for VFs.

Signed-off-by: Sudarsana Reddy Kalluru <sudarsana.kalluru@qlogic.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>