ASoC: core: no need to check return value of debugfs_create functions

When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.

Also, there is no need to store the individual debugfs file name, just
remove the whole directory all at once, saving a local variable.

Note, the soc-pcm "state" file has now moved to a subdirectory, as it is
only a good idea to save the dentries for debugfs directories, not
individual files, as the individual file debugfs functions are changing
to not return a dentry.

Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: alsa-devel@alsa-project.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20190731131716.9764-2-gregkh@linuxfoundation.org
Signed-off-by: Mark Brown <broonie@kernel.org>

include/sound/soc.h

@@ -1220,7 +1220,6 @@ struct snd_soc_card {
 
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *debugfs_card_root;
-	struct dentry *debugfs_pop_time;
 #endif
 	u32 pop_time;