staging: comedi: addi_apci_3120: remove APCI3120_DISABLE_TIMER_INT

For aesthetics, remove this define and just use ~APCI3120_ENABLE_TIMER_INT.

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>