procfs: new helper - PDE_DATA(inode)

The only part of proc_dir_entry the code outside of fs/proc
really cares about is PDE(inode)->data.  Provide a helper
for that; static inline for now, eventually will be moved
to fs/proc, along with the knowledge of struct proc_dir_entry
layout.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/net/can/proc.c b/net/can/proc.c
index 1ab8c88..b543470 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -378,7 +378,7 @@
 
 static int can_rcvlist_proc_open(struct inode *inode, struct file *file)
 {
-	return single_open(file, can_rcvlist_proc_show, PDE(inode)->data);
+	return single_open(file, can_rcvlist_proc_show, PDE_DATA(inode));
 }
 
 static const struct file_operations can_rcvlist_proc_fops = {