scsi: qla2xxx: Fix Target mode handling with Multiqueue changes.

- Fix race condition between dpc_thread accessing Multiqueue resources
  and qla2x00_remove_one thread trying to free resource.
- Fix out of order free for Multiqueue resources. Also, Multiqueue
  interrupts needs a workqueue. Interrupt needed to stop before
  the wq can be destroyed.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>