TTY: 68328serial, fix compilation

tty_struct->termios is no longer a pointer. This was changed recently
by "tty: move the termios object into the tty". But 68328serial was
not changed, so we now have a compilation error:
68328serial.c: In function 'change_speed':
68328serial.c:518:22: error: invalid type argument of '->' (have 'struct ktermios')
68328serial.c: In function 'rs_set_ldisc':
68328serial.c:620:31: error: invalid type argument of '->' (have 'struct ktermios')
68328serial.c: In function 'rs_set_termios':
68328serial.c:988:20: error: invalid type argument of '->' (have 'struct ktermios')

Fix that now.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>