scsi: lpfc: Correct target queue depth application changes

The max_scsicmpl_time parameter can be used to perform scsi cmd queue
depth mgmt based on io completion time: the queue depth is reduced to
make completion time shorter. However, as soon as an io completes and
the completion time is within limits, the code immediately bumps the
queue depth limit back up to the target queue depth. Thus the procedure
restarts, effectively limiting the usefulness of adjusting queue depth
to help completion time.

This patch makes the following changes:

 - Removes the code at io completion that resets the queue depth as soon
   as within limits.

 - As the code removed was where the target queue depth was first
   applied, change target queue depth application so that it occurs when
   the parameter is changed.

 - Makes target queue depth a standard parameter: both a module
   parameter and a sysfs parameter.

 - Optimizes the command pending count by using atomics rather than
   locks.

 - Updates the debugfs nodelist stats to allow better debugging of
   pending command counts.

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>

drivers/scsi/lpfc/lpfc.h

@@ -64,8 +64,6 @@ struct lpfc_sli2_slim;
 #define LPFC_IOCB_LIST_CNT	2250	/* list of IOCBs for fast-path usage. */
 #define LPFC_Q_RAMP_UP_INTERVAL 120     /* lun q_depth ramp up interval */
 #define LPFC_VNAME_LEN		100	/* vport symbolic name length */
-#define LPFC_TGTQ_INTERVAL	40000	/* Min amount of time between tgt
-					   queue depth change in millisecs */
 #define LPFC_TGTQ_RAMPUP_PCENT	5	/* Target queue rampup in percentage */
 #define LPFC_MIN_TGT_QDEPTH	10
 #define LPFC_MAX_TGT_QDEPTH	0xFFFF