usb: fix null deferences in low level usb serial

The hw interface drivers for the usb serial devices deference the tty
structure to set up the parameters for the initial console.  The tty
structure should be passed as a parameter to the set_termios() call.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>