staging: comedi: adv_pci1710: remove 'has_di_do' boardinfo

This member of the boardinfo isn't really necessary. All the boards
except the pci1713 have 16 digital inputs and 16 digital outputs.

There is already a 'is_pci1713' member in the boardinfo so that can
be used to determine the subdevices for the digital inputs and outputs
need to be allocated and initialized.

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>