net: more #ifdef CONFIG_COMPAT

All users of struct proto::compat_[gs]etsockopt and
struct inet_connection_sock_af_ops::compat_[gs]etsockopt are under
#ifdef already, so use it in structure definition too.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>