ASoC: Revert "samsung: Remove unneeded initialization of chan_name"

This reverts commit cdaf9af1
which breaks I2S support on the non-DT Samsung SoC platforms,
since the default "tx", "rx" DMA channel names for playback
and capture streams or custom channel names in struct
snd_dmaengine_pcm_config are supported in the ASoC dmaengine
module only for devicetree booting case.

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