staging: comedi: addi_apci_3120: clarify AI subdevice init

The two boards supported by this driver use the same functions for
the comedi operations. Remove this data from the boardinfo to clarify
the subdevice init.

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