staging: comedi: amplc_dio200: remove unnecessary local variable

The local variable 'irq' is not necessary in dio200_attach(). Just
pass the it->options[1] value directly.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>