ASoC: dmaengine_pcm: Setup device_fc in snd_hwparams_to_dma_slave_config

Usually device_fc should be set to false for audio DMAs. Initialize it in a
common place so drivers don't have to do this manually.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>