USB: cp210x: fix up set_termios variables

[Based on a patch from Johan, mangled by gregkh to keep things in line]

Fix up the variable usage in the set_termios call.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Cc: Preston Fick <preston.fick@silabs.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>