staging: comedi: pcmuio: sample types are unsigned

Sample values in comedi are generally represented as unsigned values.
Change `pcmuio_handle_intr_subdev()` in the "pcmuio" module to use
unsigned sample values for consistency.

Also, make the order in which `pcmuio_handle_intr_subdev()` writes the
two sample values (each actually containing up to 16 1-bit sample
values) independent of the host byte ordering.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>