[SCSI] libsas: remove ata_port.lock management duties from lldds

Each libsas driver (mvsas, pm8001, and isci) has invented a different
method for managing the ap->lock.  The lock is held by the ata
->queuecommand() path.  mvsas drops it prior to acquiring any internal
locks which allows it to hold its internal lock across calls to
task->task_done().  This capability is important as it is the only way
the driver can flush task->task_done() instances to guarantee that it no
longer has any in-flight references to a domain_device at
->lldd_dev_gone() time.

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

drivers/scsi/pm8001/pm8001_sas.c

@@ -364,7 +364,7 @@ static int pm8001_task_exec(struct sas_task *task, const int num,
 	struct pm8001_ccb_info *ccb;
 	u32 tag = 0xdeadbeef, rc, n_elem = 0;
 	u32 n = num;
-	unsigned long flags = 0, flags_libsas = 0;
+	unsigned long flags = 0;
 
 	if (!dev->port) {
 		struct task_status_struct *tsm = &t->task_status;
@@ -388,11 +388,7 @@ static int pm8001_task_exec(struct sas_task *task, const int num,
 				ts->stat = SAS_PHY_DOWN;
 
 				spin_unlock_irqrestore(&pm8001_ha->lock, flags);
-				spin_unlock_irqrestore(dev->sata_dev.ap->lock,
-						flags_libsas);
 				t->task_done(t);
-				spin_lock_irqsave(dev->sata_dev.ap->lock,
-					flags_libsas);
 				spin_lock_irqsave(&pm8001_ha->lock, flags);
 				if (n > 1)
 					t = list_entry(t->list.next,