staging: comedi: adv_pci_dio: cleanup PCI-1762 interrupt registers

For aesthetics, use a common define for the interrupt control and status
registers.

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>