USB: HSO: make tty_operations const

As recommended by Arjan.

Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Andrew Bird <ajb@spheresystems.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/net/usb/hso.c

@@ -2725,7 +2725,7 @@ static int hso_mux_submit_intr_urb(struct hso_shared_int *shared_int,
 }
 
 /* operations setup of the serial interface */
-static struct tty_operations hso_serial_ops = {
+static const struct tty_operations hso_serial_ops = {
 	.open = hso_serial_open,
 	.close = hso_serial_close,
 	.write = hso_serial_write,