staging: comedi: adv_pci_dio: reset digital outputs in subdevice init

Currently the board reset function also resets the digital output channels
to 0. This works but it makes the reset function a bit messy and each
board type has to be handled special.

Move the digital output reset into the subdevice init where it can be
handle based on the subdevice setup.

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>