ALSA: hda - Add power on/off counter

Added the power on/off counter and expose via sysfs files.
The sysfs files, power_on_acct and power_off_acct, are created under
each codec hwdep sysfs directory (e.g. /sys/class/sound/hwC0D0).
The files show the msec length of the codec power-on and power-off,
respectively.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_local.h b/sound/pci/hda/hda_local.h
index 461e0c1..015fbac 100644
--- a/sound/pci/hda/hda_local.h
+++ b/sound/pci/hda/hda_local.h
@@ -437,6 +437,15 @@
 static inline int snd_hda_create_hwdep(struct hda_codec *codec) { return 0; }
 #endif
 
+#ifdef CONFIG_SND_HDA_POWER_SAVE
+int snd_hda_hwdep_add_power_sysfs(struct hda_codec *codec);
+#else
+static inline int snd_hda_hwdep_add_power_sysfs(struct hda_codec *codec)
+{
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_SND_HDA_RECONFIG
 int snd_hda_hwdep_add_sysfs(struct hda_codec *codec);
 #else