staging: comedi: addi_apci_1564: rewrite the counter subdevice support

Like the timer, the support functions for the counter subdevice are broken.

Rewrite the code to follow the comedi API.

The new implementation is based on the (minimal) datasheet I have from
ADDI-DATA.

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>