sctp: fix warning at inet_sock_destruct() while release sctp socket

Commit 'net: Move rx skb_orphan call to where needed' broken sctp protocol
with warning at inet_sock_destruct(). Actually, sctp can do this right with
sctp_sock_rfree_frag() and sctp_skb_set_owner_r_frag() pair.

    sctp_sock_rfree_frag(skb);
    sctp_skb_set_owner_r_frag(skb, newsk);

This patch not revert the commit d55d87fd

,
instead remove the sctp_sock_rfree_frag() function.

------------[ cut here ]------------
WARNING: at net/ipv4/af_inet.c:151 inet_sock_destruct+0xe0/0x142()
Modules linked in: sctp ipv6 dm_mirror dm_region_hash dm_log dm_multipath
scsi_mod ext3 jbd uhci_hcd ohci_hcd ehci_hcd [last unloaded: scsi_wait_scan]
Pid: 1808, comm: sctp_test Not tainted 2.6.31-rc2 #40
Call Trace:
 [<c042dd06>] warn_slowpath_common+0x6a/0x81
 [<c064a39a>] ? inet_sock_destruct+0xe0/0x142
 [<c042dd2f>] warn_slowpath_null+0x12/0x15
 [<c064a39a>] inet_sock_destruct+0xe0/0x142
 [<c05fde44>] __sk_free+0x19/0xcc
 [<c05fdf50>] sk_free+0x18/0x1a
 [<ca0d14ad>] sctp_close+0x192/0x1a1 [sctp]
 [<c0649f7f>] inet_release+0x47/0x4d
 [<c05fba4d>] sock_release+0x19/0x5e
 [<c05fbab3>] sock_close+0x21/0x25
 [<c049c31b>] __fput+0xde/0x189
 [<c049c3de>] fput+0x18/0x1a
 [<c049988f>] filp_close+0x56/0x60
 [<c042f422>] put_files_struct+0x5d/0xa1
 [<c042f49f>] exit_files+0x39/0x3d
 [<c043086a>] do_exit+0x1a5/0x5dd
 [<c04a86c2>] ? d_kill+0x35/0x3b
 [<c0438fa4>] ? dequeue_signal+0xa6/0x115
 [<c0430d05>] do_group_exit+0x63/0x8a
 [<c0439504>] get_signal_to_deliver+0x2e1/0x2f9
 [<c0401d9e>] do_notify_resume+0x7c/0x6b5
 [<c043f601>] ? autoremove_wake_function+0x0/0x34
 [<c04a864e>] ? __d_free+0x3d/0x40
 [<c04a867b>] ? d_free+0x2a/0x3c
 [<c049ba7e>] ? vfs_write+0x103/0x117
 [<c05fc8fa>] ? sys_socketcall+0x178/0x182
 [<c0402a56>] work_notifysig+0x13/0x19
---[ end trace 9db92c463e789fba ]---

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>