xfrm: Fix initialize repl field of struct xfrm_state

Commit 'xfrm: Move IPsec replay detection functions to a separate file'
  (9fdc4883d92d20842c5acea77a4a21bb1574b495)
introduce repl field to struct xfrm_state, and only initialize it
under SA's netlink create path, the other path, such as pf_key,
ipcomp/ipcomp6 etc, the repl field remaining uninitialize. So if
the SA is created by pf_key, any input packet with SA's encryption
algorithm will cause panic.

    int xfrm_input()
    {
        ...
        x->repl->advance(x, seq);
        ...
    }

This patch fixed it by introduce new function __xfrm_init_state().

Pid: 0, comm: swapper Not tainted 2.6.38-next+ #14 Bochs Bochs
EIP: 0060:[<c078e5d5>] EFLAGS: 00010206 CPU: 0
EIP is at xfrm_input+0x31c/0x4cc
EAX: dd839c00 EBX: 00000084 ECX: 00000000 EDX: 01000000
ESI: dd839c00 EDI: de3a0780 EBP: dec1de88 ESP: dec1de64
 DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Process swapper (pid: 0, ti=dec1c000 task=c09c0f20 task.ti=c0992000)
Stack:
 00000000 00000000 00000002 c0ba27c0 00100000 01000000 de3a0798 c0ba27c0
 00000033 dec1de98 c0786848 00000000 de3a0780 dec1dea4 c0786868 00000000
 dec1debc c074ee56 e1da6b8c de3a0780 c074ed44 de3a07a8 dec1decc c074ef32
Call Trace:
 [<c0786848>] xfrm4_rcv_encap+0x22/0x27
 [<c0786868>] xfrm4_rcv+0x1b/0x1d
 [<c074ee56>] ip_local_deliver_finish+0x112/0x1b1
 [<c074ed44>] ? ip_local_deliver_finish+0x0/0x1b1
 [<c074ef32>] NF_HOOK.clone.1+0x3d/0x44
 [<c074ef77>] ip_local_deliver+0x3e/0x44
 [<c074ed44>] ? ip_local_deliver_finish+0x0/0x1b1
 [<c074ec03>] ip_rcv_finish+0x30a/0x332
 [<c074e8f9>] ? ip_rcv_finish+0x0/0x332
 [<c074ef32>] NF_HOOK.clone.1+0x3d/0x44
 [<c074f188>] ip_rcv+0x20b/0x247
 [<c074e8f9>] ? ip_rcv_finish+0x0/0x332
 [<c072797d>] __netif_receive_skb+0x373/0x399
 [<c0727bc1>] netif_receive_skb+0x4b/0x51
 [<e0817e2a>] cp_rx_poll+0x210/0x2c4 [8139cp]
 [<c072818f>] net_rx_action+0x9a/0x17d
 [<c0445b5c>] __do_softirq+0xa1/0x149
 [<c0445abb>] ? __do_softirq+0x0/0x149

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>