tty: Deprecate ldisc .chars_in_buffer() method

Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_tty.c

@@ -297,6 +297,7 @@ static ssize_t chars_in_buffer(struct tty_struct *tty)
 
 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
 {
+	WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
 	return chars_in_buffer(tty);
 }