staging: comedi: addi_common.c: remove i_ADDI_Detach()

The addi_apci_035 and addi_apci_1500 are the only drivers left that use
this function in addi_common.c. Remove the function an add a private
comedi_driver (*detach) function to those drivers.

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>