isci: kill isci_remote_device_change_state()

Now that "stopping/stopped" are one in the same and signalled by a NULL device
pointer the rest of the device status infrastructure can be removed (->status
and ->state_lock).  The "not ready for i/o state" is replaced with a state
flag, and is evaluated under scic_lock so that we don't see transients from
taking the device reference to submitting the i/o.

This also fixes a potential leakage of can_queue slots in the rare case that
SAS_TASK_ABORTED is set at submission.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/scsi/isci/host.c

@@ -2504,7 +2504,6 @@ int isci_host_init(struct isci_host *isci_host)
 
 		INIT_LIST_HEAD(&idev->reqs_in_process);
 		INIT_LIST_HEAD(&idev->node);
-		spin_lock_init(&idev->state_lock);
 	}
 
 	return 0;