staging: comedi: ni_mio_common: remove disabled GPCT functions

The GPCT (general purpose counter timer) is handled by the ni_tio and
ni_tiocmd modules. Remove the old disabled code in this file.

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>