create_mnt_ns: unidiomatic use of list_add()

while list_add(A, B) and list_add(B, A) are equivalent when both A and B
are guaranteed to be empty, the usual idiom is list_add(what, where),
not the other way round...  Not a bug per se, but only by accident and
it makes RTFS harder for no good reason.
Spotted-by: NRajat Sharma <fs.rajat@gmail.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/namespace.c

@@ -2463,7 +2463,7 @@ static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
 		struct mount *mnt = real_mount(m);
 		mnt->mnt_ns = new_ns;
 		new_ns->root = mnt;
-		list_add(&new_ns->list, &mnt->mnt_list);
+		list_add(&mnt->mnt_list, &new_ns->list);
 	} else {
 		mntput(m);
 	}