seq_file: fix passing wrong private data

DEFINE_PROC_SHOW_ATTRIBUTE() is supposed to be used to define a series
of functions and variables to register proc file easily. And the users
can use proc_create_data() to pass their own private data and get it
via seq->private in the callback. Unfortunately, the proc file system
use PDE_DATA() to get private data instead of inode->i_private. So fix
it. Fortunately, there only one user of it which does not pass any
private data, so this bug does not break any in-tree codes.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 97a3253 ("proc: convert everything to "struct proc_ops"")
Signed-off-by: Muchun Song <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Florent Revest <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Christian Brauner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/seq_file.h

@@ -209,7 +209,7 @@ static const struct file_operations __name ## _fops = {			\
 #define DEFINE_PROC_SHOW_ATTRIBUTE(__name)				\
 static int __name ## _open(struct inode *inode, struct file *file)	\
 {									\
-	return single_open(file, __name ## _show, inode->i_private);	\
+	return single_open(file, __name ## _show, PDE_DATA(inode));	\
 }									\
 									\
 static const struct proc_ops __name ## _proc_ops = {			\