tty: fix routine name in ptmx_open()

At ptmx_open(), the 2nd parameter for check_tty_count() should
be "ptmx_open".

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/tty_io.c

@@ -2842,7 +2842,7 @@ static int ptmx_open(struct inode *inode, struct file *filp)
 	if (devpts_pty_new(tty->link))
 		goto out1;
 
-	check_tty_count(tty, "tty_open");
+	check_tty_count(tty, "ptmx_open");
 	retval = ptm_driver->ops->open(tty, filp);
 	if (!retval)
 		return 0;