If xfrm_*_register_afinfo failed since xfrm_*_afinfo[afinfo->family] had the
value, return the -EEXIST, not -ENOBUFS
Signed-off-by: NLi RongQing <roy.qing.li@gmail.com>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>