staging: comedi: vmk80xx: save the boardinfo in the comedi_device

Save a copy of the boardinfo pointer in the comedi_device 'board_ptr'.
The subdevice functions can then simply get it using the comedi_board()
helper.

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>