sctp: get netns from asoc and ep base

Commit 312434617cb1 ("sctp: cache netns in sctp_ep_common") set netns
in asoc and ep base since they're created, and it will never change.
It's a better way to get netns from asoc and ep base, comparing to
calling sock_net().

This patch is to replace them.

v1->v2:
  - no change.

Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index e83cdaa..df60b5e 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -218,10 +218,9 @@ void sctp_stream_update(struct sctp_stream *stream, struct sctp_stream *new)
 static int sctp_send_reconf(struct sctp_association *asoc,
 			    struct sctp_chunk *chunk)
 {
-	struct net *net = sock_net(asoc->base.sk);
 	int retval = 0;
 
-	retval = sctp_primitive_RECONF(net, asoc, chunk);
+	retval = sctp_primitive_RECONF(asoc->base.net, asoc, chunk);
 	if (retval)
 		sctp_chunk_free(chunk);