[media] pxa_camera: conversion to dmaengine

Convert pxa_camera to dmaengine. This removes all DMA registers
manipulation in favor of the more generic dmaengine API.

The functional level should be the same as before. The biggest change is
in the sg_split() function, which splits a videobuf-dma into several
scatterlists for 3 planes captures (Y, U, V).

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
[g.liakhovetski@gmx.de: fix a function prototype, use bool, struct init]
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>