V4L/DVB (11322): pxa_camera: Fix overrun condition on last buffer

The last buffer queued will often overrun, as the DMA chain
is finished, and the time the dma irq handler is activated,
the QCI fifos are filled by the sensor.

The fix is to ignore the overrun condition on the last
queued buffer, and restart the capture only on intermediate
buffers of the chain.

Moreover, a fix was added to the very unlikely condition
where in YUV422P mode, one channel overruns while another
completes at the very same time. The capture is restarted
after the overrun as before, but the other channel
completion is now ignored.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>