jfs: Fix array-index-out-of-bounds in diFree

[ Upstream commit f73f969b2eb39ad8056f6c7f3a295fa2f85e313a ]

Reported-by:  <syzbot+241c815bda521982cb49@syzkaller.appspotmail.com>
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 55b732c8b09b41148eaab2fa8e31b0af47671e00)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>