scsi: libcxgbi: update route finding logic

To support vlan and bridge devices first find route using ifindex 0, if
route is not found through net device associated with input scsi host then
find route using ifindex of net device.

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