ASoC: soc-core: initialize debugfs in snd_soc_instantiate_card()

Current soc_init_card_debugfs() is called from snd_soc_register_card()
but, soc_cleanup_card_debugfs() is called from soc_cleanup_card_resources(),
not from paired function.

This differences don't matter for now. But if anyone wants to implement
a proper hotplug/unplug, this difference would become clearer.

Now, we can assume that snd_soc_instantiate_card() and
soc_cleanup_card_resources() are paired function.
soc_init_card_debugfs() / soc_cleanup_card_debugfs() paired function
should be called from these.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>