V4L/DVB (7237): Convert videobuf-dma-sg to generic DMA API

videobuf-dma-sg does not need to depend on PCI. Switch it to using generic
DMA API, convert all affected drivers, relax Kconfig restriction, improve
compile-time type checking, fix some Coding Style violations while at it.

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