md: fix problems with freeing private data after ->run failure.

If ->run() fails, it can either free the data structures it
allocated, or leave that task to ->free() which will be called
on failures.

However:
  md.c calls ->free() even if ->private_data is NULL, which
     causes problems in some personalities.
  raid0.c frees the data, but doesn't clear ->private_data,
     which will become a problem when we fix md.c

So better fix both these issues at once.

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Fixes: 5aa61f4
URL: https://bugzilla.kernel.org/show_bug.cgi?id=94381
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -5080,7 +5080,8 @@ int md_run(struct mddev *mddev)
 	}
 	if (err) {
 		mddev_detach(mddev);
-		pers->free(mddev, mddev->private);
+		if (mddev->private)
+			pers->free(mddev, mddev->private);
 		module_put(pers->owner);
 		bitmap_destroy(mddev);
 		return err;

drivers/md/raid0.c

@@ -467,8 +467,6 @@ static int raid0_run(struct mddev *mddev)
 	dump_zones(mddev);
 
 	ret = md_integrity_register(mddev);
-	if (ret)
-		raid0_free(mddev, conf);
 
 	return ret;
 }