ASoC: samsung: Remove unneeded initialization of chan_name

This patch updates the I2S drivers to always use chan_names[] field
of struct snd_dmaengine_pcm_config for specifying DMA channel names,
rather than using struct snd_dmaengine_dai_dma_data.

This allows us to subsequently drop the
SND_DMAENGINE_PCM_FLAG_CUSTOM_CHANNEL_NAME flag, now when the last
use of that flag is removed.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>