V4L/DVB (7670): pxa-camera: handle FIFO overruns

FIFO overruns are not seldom on PXA camera interface FIFOs. Handle them by
dropping the corrupted frame, waiting for the next start-of-frame, and
restarting capture.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>