staging: comedi: addi_apci_1564: define the APCI1564_DO_IRQ_REG bits

Define the bits in this register.

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>