scsi: libcxgbi: in case of vlan pass 0 as ifindex to find route

In case of vlan pass 0 as ifindex to find route instead of passing
real_dev ifindex, if we pass real_dev ifindex then
ip_route_output_ports() and ip6_route_output() will check for route
through real_dev not through vlan interface.

Signed-off-by: Varun Prakash <varun@chelsio.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>