ASoC: soc-core: define soc_dpcm_debugfs_add() for non CONFIG_DEBUG_FS

ASoC: soc-core: define soc_dpcm_debugfs_add() for non CONFIG_DEBUG_FS

soc_dpcm_debugfs_add() is implemented at soc-pcm.c under CONFIG_DEBUG_FS.
Thus, soc-core.c which is only user of it need to use CONFIG_DEBUG_FS, too.

This patch defines soc_dpcm_debugfs_add() for non CONFIG_DEBUG_FS case.
Then, we can remove #ifdef CONFIG_DEBUG_FS from soc-core.c

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/875zn9ahnv.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>