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/drivers/acpi/battery.c b/drivers/acpi/battery.c
index c5cd5b5..169ced7 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -929,7 +929,7 @@
 } \
 static int acpi_battery_##_name##_open_fs(struct inode *inode, struct file *file) \
 { \
-	return single_open(file, acpi_battery_read_##_name, PDE(inode)->data); \
+	return single_open(file, acpi_battery_read_##_name, PDE_DATA(inode)); \
 }
 
 DECLARE_FILE_FUNCTIONS(info);