[NET]: Unexport sock_enable_timestamp().

sock_enable_timestamp() no longer has any modular users.
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -1649,7 +1649,6 @@ void sock_enable_timestamp(struct sock *sk)
 		net_enable_timestamp();
 	}
 }
-EXPORT_SYMBOL(sock_enable_timestamp);
 
 /*
  *	Get a socket option on an socket.