solo6x10: Conversion to videobuf-dma-sg (from dma-cont)

Full rewrite of the P2M DMA Engine to support scatter gather and take
advantage of some of the features of the hardware. This includes using
repeat DMA operations and line-mode transfers (for copying OSG and
video display buffers).

What isn't working: For some reason, descriptor mode is not working. I've
implemented a psuedo version (still has one-interrupt per DMA operation),
but we would get huge improvements if we could hand off a ring of
descriptors to the P2M and get back one interrupt when it was done with
all of them.

Documentation is very vague on this, and even the ODM example code
half attempts to get it right, but comments it out of the driver
because it just doesn't work *sigh*

Converts all v4l2 to dma-sg. So long slow dma-contiguous, but hello
more interrupts :(

Signed-off-by: Ben Collins <bcollins@bluecherry.net>