staging: comedi: adv_pci1723: remove boardinfo

This driver only supports one board type. Remove the boardinfo and
associated code.

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>