nilfs2: update comment on deactivate_super at nilfs_get_sb

deactivate_super was replaced with deactivate_locked_super, but the
comment of nilfs_get_sb remain unchanged.  This renews the comment.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 6b05771..c88e664 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -1106,7 +1106,7 @@
 	put_nilfs(nilfs);
 	deactivate_locked_super(s);
 	/*
-	 * deactivate_super() invokes close_bdev_exclusive().
+	 * deactivate_locked_super() invokes close_bdev_exclusive().
 	 * We must finish all post-cleaning before this call;
 	 * put_nilfs() needs the block device.
 	 */