staging: comedi: ni_660x: initialize the counter with the subdevice init

Remove the extra for loop and just initialize the counter as the subdevices
are created.

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>