UPSTREAM: net: xfrm: fix memory leak in xfrm_user_rcv_msg

Syzbot reported memory leak in xfrm_user_rcv_msg(). The
problem was is non-freed skb's frag_list.

In skb_release_all() skb_release_data() will be called only
in case of skb->head != NULL, but netlink_skb_destructor()
sets head to NULL. So, allocated frag_list skb should be
freed manualy, since consume_skb() won't take care of it

Fixes: 5106f4a8acff ("xfrm/compat: Add 32=>64-bit messages translator")
Reported-and-tested-by:  <syzbot+fb347cf82c73a90efcca@syzkaller.appspotmail.com>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
(cherry picked from commit 7c1a80e80cde008f271bae630d28cf684351e807)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ib58ea510bffcc4afe301b2ded4e644d07aeb9771