USB: serial: kl5kusb105: remove unused termios structure

Remove unused termios structure from private data that was left by an
earlier purge by commit b1cff285 ("usb serial: Eliminate bogus ioctl
code").

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>