scsi: avoid ->change_queue_depth indirection for queue full tracking

All drivers use the implementation for ramping the queue up and down, so
instead of overloading the change_queue_depth method call the
implementation diretly if the driver opts into it by setting the
track_queue_depth flag in the host template.

Note that a few drivers validated the new queue depth in their
change_queue_depth method, but as we never go over the queue depth
set during slave_configure or the sysfs file this isn't nessecary
and can safely be removed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Venkatesh Srinivas <venkateshs@google.com>

drivers/scsi/pm8001/pm8001_init.c

@@ -90,6 +90,7 @@ static struct scsi_host_template pm8001_sht = {
 	.ioctl			= sas_ioctl,
 	.shost_attrs		= pm8001_host_attrs,
 	.use_blk_tags		= 1,
+	.track_queue_depth	= 1,
 };
 
 /**