be2net: don't report EVB for older chipsets when SR-IOV is disabled

The EVB (virtual bridge) functionality should be disabled on older BE3
and Lancer chips if SR-IOV is disabled in the NIC's BIOS. This setting
is identified by the zero value of total VFs reported by the card.
The GET_HSW_CONFIG command cannot be used as it is not supported by
these older chipset's FW.

v2: added the comment

Cc: Sathya Perla <sathya.perla@broadcom.com>
Cc: Ajit Khaparde <ajit.khaparde@broadcom.com>
Cc: Padmanabh Ratnakar <padmanabh.ratnakar@broadcom.com>
Cc: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Cc: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Acked-by: Sathya Perla <sathya.perla@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>