staging: comedi: addi_apci_3120: simplify analog input boardinfo

There are two boards supported by this driver. One with 16-bit analog
inputs and the other 12-bit analog inputs.

Add a bit field flag, 'ai_is_16bit', to the boardinfo and remove the
'i_AiMaxdata' member. Use the new flag to initialize tne analog input
subdevice maxdata correctly.

For aesthetics, adjust the whitespace in the boardinfo declaration.

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>