tty: Convert termios_mutex to termios_rwsem

termios is commonly accessed unsafely (especially by N_TTY)
because the existing mutex forces exclusive access.
Convert existing usage.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index c677829..02af6cc 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -828,7 +828,7 @@
  *	If the caller passes a tty structure then update the termios winsize
  *	information and perform any necessary signal handling.
  *
- *	Caller must hold the console semaphore. Takes the termios mutex and
+ *	Caller must hold the console semaphore. Takes the termios rwsem and
  *	ctrl_lock of the tty IFF a tty is passed.
  */
 
@@ -972,7 +972,7 @@
  *	the actual work.
  *
  *	Takes the console sem and the called methods then take the tty
- *	termios_mutex and the tty ctrl_lock in that order.
+ *	termios_rwsem and the tty ctrl_lock in that order.
  */
 static int vt_resize(struct tty_struct *tty, struct winsize *ws)
 {