staging: comedi: pcmuio: fix types of some private data variables

The 'enabled_mask' is a bit mask of the channels that are enabled
for interrupt detection and should be an unsigned int.

The 'stop_count' is a >= 0 value that is set by the unsigned int
cmd->stop_arg. Make it an unsigned int.

The 'active' and 'continuous' members are flags. Make them unsigned
int bit-fields to save a bit of space.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>