proc: consolidate per-net single_open callers

There are already 7 of them - time to kill some duplicate code.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/seq_file_net.h b/include/linux/seq_file_net.h
index 4ac5254..87dcc0e 100644
--- a/include/linux/seq_file_net.h
+++ b/include/linux/seq_file_net.h
@@ -14,6 +14,8 @@
 
 int seq_open_net(struct inode *, struct file *,
 		 const struct seq_operations *, int);
+int single_open_net(struct inode *, struct file *file,
+		int (*show)(struct seq_file *, void *));
 int seq_release_net(struct inode *, struct file *);
 static inline struct net *seq_file_net(struct seq_file *seq)
 {