staging: comedi: adv_pci1710: refactor boardinfo 'cardtype'

The 'cardtype' in the boardinfo is only used to:

 1) determine if the board is a pci1720 during the attach of the driver
    and when reseting the board
 2) determine is the board is not a pci1713 when checking for analog input
    data dropout

There is also an unnecessary use of the 'cardtype' when canceling an analog
input async command.

Remove the 'cardtype' member and add two bit-field flags, 'is_pci1713' and
'is_pci1720'. Refactor the driver to use the new flags.

Remove the unnecessary cardtype handling in pci171x_ai_cancel().

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>