scsi: scsi_dh: Document alua_rtpg_queue() arguments

Since commit 3a025e1d1c ("Add optional check for bad kernel-doc
comments") building with W=1 causes warnings to appear for issues in
kernel-doc headers. This patch avoids that the following warnings are
reported when building with W=1:

drivers/scsi/device_handler/scsi_dh_alua.c:867: warning: No description found for parameter 'pg'
drivers/scsi/device_handler/scsi_dh_alua.c:867: warning: No description found for parameter 'sdev'
drivers/scsi/device_handler/scsi_dh_alua.c:867: warning: No description found for parameter 'qdata'
drivers/scsi/device_handler/scsi_dh_alua.c:867: warning: No description found for parameter 'force'

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/device_handler/scsi_dh_alua.c

@@ -876,6 +876,11 @@ static void alua_rtpg_work(struct work_struct *work)
 
 /**
  * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
+ * @pg: ALUA port group associated with @sdev.
+ * @sdev: SCSI device for which to submit an RTPG.
+ * @qdata: Information about the callback to invoke after the RTPG.
+ * @force: Whether or not to submit an RTPG if a work item that will submit an
+ *         RTPG already has been scheduled.
  *
  * Returns true if and only if alua_rtpg_work() will be called asynchronously.
  * That function is responsible for calling @qdata->fn().