V4L/DVB (8611): Add suspend/resume to pxa_camera driver

PXA suspend switches off DMA core, which loses all context
of previously assigned descriptors. As pxa_camera driver
relies on DMA transfers, setup the lost descriptors on
resume and retrigger frame acquisition if needed.

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@infradead.org>