nilfs2: fix memory leak in nilfs_ioctl_clean_segments

This fixes a new memory leak problem in garbage collection.  The
problem was brought by the bugfix patch ("nilfs2: fix lock order
reversal in nilfs_clean_segments ioctl").

Thanks to Kentaro Suzuki for finding this problem.

Reported-by: Kentaro Suzuki <k_suzuki@ms.sylc.co.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 50ff3f2..d6759b9 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -576,7 +576,7 @@
 	ret = nilfs_clean_segments(inode->i_sb, argv, kbufs);
 
  out_free:
-	while (--n > 0)
+	while (--n >= 0)
 		vfree(kbufs[n]);
 	kfree(kbufs[4]);
 	return ret;