staging: comedi: pcmmio: tidy up pcmmio_handle_dio_intr()

Refactor the code to remove some of the indent levels.

Remove 'mytrig', the shift and mask end up making it the same as 'triggered'
anyway.

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>