md: rename ->stop to ->free

Now that the ->stop function only frees the private data,
rename is accordingly.

Also pass in the private pointer as an arg rather than using
mddev->private.  This flexibility will be useful in level_store().

Finally, don't clear ->private.  It doesn't make sense to clear
it seeing that isn't what we free, and it is no longer necessary
to clear ->private (it was some time ago before  ->to_remove was
introduced).

Setting ->to_remove in ->free() is a bit of a wart, but not a
big problem at the moment.

Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 4825260..dab908b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6313,14 +6313,12 @@
 	return -EIO;
 }
 
-static int stop(struct mddev *mddev)
+static void raid5_free(struct mddev *mddev, void *priv)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf = priv;
 
 	free_conf(conf);
-	mddev->private = NULL;
 	mddev->to_remove = &raid5_attrs_group;
-	return 0;
 }
 
 static void status(struct seq_file *seq, struct mddev *mddev)
@@ -7094,7 +7092,7 @@
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= raid5_free,
 	.status		= status,
 	.error_handler	= error,
 	.hot_add_disk	= raid5_add_disk,
@@ -7118,7 +7116,7 @@
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= raid5_free,
 	.status		= status,
 	.error_handler	= error,
 	.hot_add_disk	= raid5_add_disk,
@@ -7143,7 +7141,7 @@
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= raid5_free,
 	.status		= status,
 	.error_handler	= error,
 	.hot_add_disk	= raid5_add_disk,