ASoC: dma: Generic ASoC dmaengine driver enhancements

This is the work so far on dmaengine for v3.14, it is being cross merged
into the Tegra tree to support a large DMA overhaul there.  The main
additions are a change in the DMA request API which allows better
interaction at system startup using deferred probes and methods for
overriding the default device and channel names used to request DMA.