ASoC: soc-pcm: add dpcm_create/remove_debugfs_state()

soc-pcm.c has implementation which depends on CONFIG_DEBUG_FS.
But, we don't want to have random #ifdef.
This patch adds dpcm_create/remove_debugfs_state() and care it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/877e0jjc9b.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>