scsi: libcxgbi: use ndev->ifindex to find route

If cxgbi_ep_connect() is called with valid shost then find associated
ndev and use ndev->ifindex to find route.

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