net: make ->{get,set}sockopt in proto_ops optional

Just check for a NULL method instead of wiring up
sock_no_{get,set}sockopt.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/appletalk/ddp.c

@@ -1917,8 +1917,6 @@ static const struct proto_ops atalk_dgram_ops = {
 #endif
 	.listen		= sock_no_listen,
 	.shutdown	= sock_no_shutdown,
-	.setsockopt	= sock_no_setsockopt,
-	.getsockopt	= sock_no_getsockopt,
 	.sendmsg	= atalk_sendmsg,
 	.recvmsg	= atalk_recvmsg,
 	.mmap		= sock_no_mmap,