ASoC: hisilicon: Use devm_snd_soc_register_component

Per feedback from Mark Brown, this patch updates the hi6210-i2s
driver to use devm_snd_soc_register_component which simplifies
the logic a bit.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>