staging: comedi: pcmmio: remove unnecessary for () loop and sanity check

There is only one asic on the board so the for () loop in the interrupt
handler to check multiple asics is not needed.

The sanity check of the 'irq' in the interrupt handler is also not needed.
If it _is_ wrong we have bigger problems in the kernel.

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>