staging: comedi: addi_common.h: remove ADDI_{EN, DIS}ABLE defines

These defines don't add any additional clarity to the addi_data drivers.
They are also only used in the addi_apci_3120 driver. Just remove them.

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>