scsi: lpfc: Fix lingering lpfc_wq resource after driver unload

After driver unloads, lpfc_wq remains active. The destroy_workqueue
calls were not being made in driver unload.  Additionally, SLI3 is
allocating lpfc_wq resources, but never uses it.

Make the destroy_workqueue calls on driver unload.  Modify the SLI3 code
path no longer allocate lpfc_wq resources.

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>