staging: comedi: pcmuio: return void from pcmuio_start_intr()

This function always returns '0' so the comedi_event() is never done by the
callers.

Change the return type to void and remove the comedi_event() dead code.

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>