tty: fix up usb serial console for termios change.

fixes these errors:

drivers/usb/serial/console.c: In function 'usb_console_setup':
drivers/usb/serial/console.c:168:16: error: invalid type argument of '->' (have 'struct ktermios')
drivers/usb/serial/console.c:169:4: error: incompatible type for argument 1 of 'tty_termios_encode_baud_rate'
include/linux/tty.h:449:13: note: expected 'struct ktermios *' but argument is of type 'struct ktermios'

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>