ocfs2: release the buffer head in ocfs2_do_truncate.

In ocfs2_do_truncate, we forget to release last_eb_bh which
will cause memleak. So call brelse in the end.
Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/alloc.c

@@ -6851,7 +6851,7 @@ static int ocfs2_do_truncate(struct ocfs2_super *osb,
 	}
 	status = 0;
 bail:
-
+	brelse(last_eb_bh);
 	mlog_exit(status);
 	return status;
 }