staging: comedi: adl_pci9118: introduce pci9118_amcc_int_ena()

Introduce a helper function to program the AMCC interrupt control/
status register to enable/disable interrupts.

Fix the analog input (*cancel). The analog input async command support
is the only interrupt generator. The (*cancel) should always disable
interrupts.

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>