ASoC: atmel: sam9x5_wm8731: use devm_snd_soc_register_card()

Using devm_snd_soc_register_card() can make the code
shorter and cleaner.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20210602141619.323286-1-yangyingliang@huawei.com


Signed-off-by: Mark Brown <broonie@kernel.org>