ipv6: rename datagram_send_ctl and datagram_recv_ctl

The datagram_*_ctl functions in net/ipv6/datagram.c are IPv6-specific.  Since
datagram_send_ctl is publicly exported it should be appropriately named to
reflect the fact that it's for IPv6 only.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sunrpc/svcsock.c

@@ -465,7 +465,7 @@ static int svc_udp_get_dest_address4(struct svc_rqst *rqstp,
 }
 
 /*
- * See net/ipv6/datagram.c : datagram_recv_ctl
+ * See net/ipv6/datagram.c : ip6_datagram_recv_ctl
  */
 static int svc_udp_get_dest_address6(struct svc_rqst *rqstp,
 				     struct cmsghdr *cmh)