scsi: qedf: Use discovery list to traverse rports

The list of rports might become stale so we should rather traverse the
discovery list when trying relogin.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>