staging: comedi: addi_apci_2200: use addi_watchdog module

The current watchdog support in hwdrv_apci2200.c does not conform
to the comedi API.

Use the addi_watchdog module to provide support for the watchdog
subdevice and remove the now unneeded hwdrv_apci2200.c file.

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>