scsi: lpfc: Fix system crash when port is reset.

The driver panic when using the els_wq during port reset.

Check for NULL els_wq before dereferencing.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>