staging: comedi: pcl816: consolidate the interrupt code

This driver only supports interrupt driven DMA transfers for async
command support. Absorb the interrupt_pcl816_ai_mode13_dma() helper
into the interrupt handler to clarify the code.

At some point during the interrupt, comedi_event() is called to pass
any events to the comedi subsystem. Move this to the interrupt handler.
Add a comedi_event() call to pcl816_ai_poll() due to the removal of
the call from transfer_from_dma_buf().

For aesthetics, rename the interrupt function so it has namespace
associated with the driver.

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>