USB: whiteheat: fix broken port configuration

commit 9eecf22d2b375b9064a20421c6c307b760b03d46 upstream.

When configuring the port (e.g. set_termios) the port minor number
rather than the port number was used in the request (and they only
coincide for minor number 0).

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>