USB: kl5kusb105: Remove klsi_105_tiocmset function

This patch remove the function klsi_105_tiocmset which was only
returning -EINVAL. It also removes the function prototype and
the .tiocmset entry in the struct usb_serial_driver.

Verified by compilation only.

Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>