usb-serial: begin switching to ->[sg]et_serial()

add such methods for usb_serial_driver, provide tty_operations
->[sg]et_serial() calling those.  For now the lack of methods
in driver means ENOIOCTLCMD from usb-serial ->[sg]et_serial(),
making tty_ioctl() fall back to calling ->ioctl().  Once all
drivers are converted, we'll be returning -ENOTTY instead,
completing the switchover.

Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index 106551a..1c19f77 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -285,6 +285,8 @@ struct usb_serial_driver {
 	int  (*write_room)(struct tty_struct *tty);
 	int  (*ioctl)(struct tty_struct *tty,
 		      unsigned int cmd, unsigned long arg);
+	int  (*get_serial)(struct tty_struct *tty, struct serial_struct *ss);
+	int  (*set_serial)(struct tty_struct *tty, struct serial_struct *ss);
 	void (*set_termios)(struct tty_struct *tty,
 			struct usb_serial_port *port, struct ktermios *old);
 	void (*break_ctl)(struct tty_struct *tty, int break_state);