tcp: remove dead code in __tcp_v6_send_check()

For some reason, I forgot to change __tcp_v6_send_check() at
the same time I removed (ip_summed == CHECKSUM_PARTIAL) check
in __tcp_v4_send_check()

Fixes: 98be9b12 ("tcp: remove dead code after CHECKSUM_PARTIAL adoption")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_checksum.h

@@ -65,15 +65,9 @@ static inline void __tcp_v6_send_check(struct sk_buff *skb,
 {
 	struct tcphdr *th = tcp_hdr(skb);
 
-	if (skb->ip_summed == CHECKSUM_PARTIAL) {
-		th->check = ~tcp_v6_check(skb->len, saddr, daddr, 0);
-		skb->csum_start = skb_transport_header(skb) - skb->head;
-		skb->csum_offset = offsetof(struct tcphdr, check);
-	} else {
-		th->check = tcp_v6_check(skb->len, saddr, daddr,
-					 csum_partial(th, th->doff << 2,
-						      skb->csum));
-	}
+	th->check = ~tcp_v6_check(skb->len, saddr, daddr, 0);
+	skb->csum_start = skb_transport_header(skb) - skb->head;
+	skb->csum_offset = offsetof(struct tcphdr, check);
 }
 
 static inline void tcp_v6_gso_csum_prep(struct sk_buff *skb)