staging: comedi: pcl711: remove 'is_pcl711b' from boardinfo

This member in the board info is used to indicate if the board is
a PCL711B. This board uses bits in the mode register to select the
IRQ used for interrupts. These bits do nothing on the other boards
supported by this driver.

Remove the 'is_pcl711b' variable from the boardinfo. Also, remove
the 'mode' variable from the private data and just calculate the
mode bits when needed.

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>