inet: do not export inet_gro_{receive|complete}

inet_gro_receive() and inet_gro_complete() are part
of GRO engine which can not be modular.

Similarly, inet_gso_segment() does not need to be exported,
being part of GSO stack.

In other words, net/ipv6/ip6_offload.o is part of vmlinux,
regardless of CONFIG_IPV6.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20210202154145.1568451-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/af_inet.c

@@ -1419,7 +1419,6 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 out:
 	return segs;
 }
-EXPORT_SYMBOL(inet_gso_segment);
 
 static struct sk_buff *ipip_gso_segment(struct sk_buff *skb,
 					netdev_features_t features)
@@ -1550,7 +1549,6 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
 
 	return pp;
 }
-EXPORT_SYMBOL(inet_gro_receive);
 
 static struct sk_buff *ipip_gro_receive(struct list_head *head,
 					struct sk_buff *skb)
@@ -1636,7 +1634,6 @@ int inet_gro_complete(struct sk_buff *skb, int nhoff)
 
 	return err;
 }
-EXPORT_SYMBOL(inet_gro_complete);
 
 static int ipip_gro_complete(struct sk_buff *skb, int nhoff)
 {