ASoC: mxs: move to use generic DMA helper

With mxs-dma converted to generic DMA bindings, let's move mxs-pcm to
use it by removing flages SND_DMAENGINE_PCM_FLAG_NO_DT and
SND_DMAENGINE_PCM_FLAG_COMPAT.  As the result, those mxs custom dma
params code can be removed now.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>