ASoC: davinci-mcasp: Deprecate the use of davinci-pcm in favor of edma-pcm

The edma-pcm performs as good as the old davinci-pcm and it's use does not
require the 'ping-pong' mode of davinci-pcm, which was introduced to
overcome under/over flow issues when using davinci-pcm.

Keep the SND_DAVINCI_SOC config option to select the SND_EDMA_SOC to avoid
regression in audio support.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>