[SOCKET]: Export __sock_recv_timestamp

Kernel: arch/x86_64/boot/bzImage is ready  (#2)
  MODPOST 1816 modules
WARNING: "__sock_recv_timestamp" [net/sctp/sctp.ko] undefined!
WARNING: "__sock_recv_timestamp" [net/packet/af_packet.ko] undefined!
WARNING: "__sock_recv_timestamp" [net/key/af_key.ko] undefined!
WARNING: "__sock_recv_timestamp" [net/ipv6/ipv6.ko] undefined!
WARNING: "__sock_recv_timestamp" [net/atm/atm.ko] undefined!
make[2]: *** [__modpost] Error 1
make[1]: *** [modules] Error 2
make: *** [_all] Error 2

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>