ASoC: zx296702-i2s: Fix resource leak when unload module

Use devm_* API to fix leaks in current code.
1. Use devm_kzalloc to fix memory leak for zx_i2s when unload the module.
2. Use devm_snd_soc_register_component to ensure component is unregistered
   when unload the module.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Jun Nie <jun.nie@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>