staging: comedi: addi_apci_1564: remove unused static variables

The global variables ui_InterruptStatus_1564 and ui_InterruptData are both
set but never used.  Just remove them from the driver.

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