net/tcp: switch ->md5_parse to sockptr_t

Pass a sockptr_t to prepare for set_fs-less handling of the kernel
pointer from bpf-cgroup.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -2002,7 +2002,7 @@ struct tcp_sock_af_ops {
 					 const struct sk_buff *skb);
 	int		(*md5_parse)(struct sock *sk,
 				     int optname,
-				     char __user *optval,
+				     sockptr_t optval,
 				     int optlen);
 #endif
 };