[JFFS2] Track parent inode for directories (for NFS export)

To support NFS export, we need to know the parent inode of directories.
Rather than growing the jffs2_inode_cache structure, share space with
the nlink field -- which was always set to 1 for directories anyway.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/fs/jffs2/erase.c b/fs/jffs2/erase.c
index 25a640e..5e86f43 100644
--- a/fs/jffs2/erase.c
+++ b/fs/jffs2/erase.c
@@ -294,7 +294,7 @@
 			break;
 #endif
 		default:
-			if (ic->nodes == (void *)ic && ic->nlink == 0)
+			if (ic->nodes == (void *)ic && ic->pino_nlink == 0)
 				jffs2_del_ino_cache(c, ic);
 	}
 }