staging: comedi: ni_660x: tidy up ni_gpct_{write, read}_register()

Rename these functions so they have namespace associated with the
driver.

Fix the checkpatch.pl issues:

WARNING: Prefer 'unsigned int' to bare use of 'unsigned'

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>