staging: comedi: icp_multi: remove counter subdevice

The support functions for this subdevice are not complete. Since the
counter is the last subdevice just remove it and it's allocation.

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>