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/fs/proc/generic.c b/fs/proc/generic.c
index 51fcb20..c0ad720 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -346,7 +346,7 @@
 
 static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
-	nd_set_link(nd, PDE(dentry->d_inode)->data);
+	nd_set_link(nd, PDE_DATA(dentry->d_inode));
 	return NULL;
 }