ipv6: remove inet6_rsk() and tcp_twsk_ipv6only()

The stubs under !CONFIG_IPV6 were missed when real functions
got deleted ca. v3.13.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -371,19 +371,12 @@ static inline struct ipv6_pinfo * inet6_sk(const struct sock *__sk)
 	return NULL;
 }
 
-static inline struct inet6_request_sock *
-			inet6_rsk(const struct request_sock *rsk)
-{
-	return NULL;
-}
-
 static inline struct raw6_sock *raw6_sk(const struct sock *sk)
 {
 	return NULL;
 }
 
 #define inet6_rcv_saddr(__sk)	NULL
-#define tcp_twsk_ipv6only(__sk)		0
 #define inet_v6_ipv6only(__sk)		0
 #endif /* IS_ENABLED(CONFIG_IPV6) */
 #endif /* _IPV6_H */