tty: n_tty: simplify chars_in_buffer()

The 'if' in chars_in_buffer() is misleadingly inverted. And since the
only difference is the head used for computation, cache the head using
ternary operator. And use that in return directly.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Jiri Slaby (SUSE)

drivers/tty/n_tty.c

@@ -219,13 +219,9 @@ static void n_tty_kick_worker(const struct tty_struct *tty)
 static ssize_t chars_in_buffer(const struct tty_struct *tty)
 {
 	const struct n_tty_data *ldata = tty->disc_data;
-	ssize_t n = 0;
+	size_t head = ldata->icanon ? ldata->canon_head : ldata->commit_head;
 
-	if (!ldata->icanon)
-		n = ldata->commit_head - ldata->read_tail;
-	else
-		n = ldata->canon_head - ldata->read_tail;
-	return n;
+	return head - ldata->read_tail;
 }
 
 /**