staging: comedi: adv_pci1723: remove devpriv and this_board macros

The devpriv macro relies on a local variable having a specific name.
Remove it.

The this_board macro in this driver is a bit different in this driver.
In other comedi drivers, this macro returns the dev->board_ptr. In this
driver its simply 'boardtypes' which returns the first boardinfo element.
Remove this macro also by making sure the dev->board_ptr is set in the
pci1723_find_pci_dev() function and using the comedi_board() helper
to get the pointer in pci1723_attach().

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>