ASoC: dapm: Fix _PRE and _POST events for DAPM performance improvements

Ever since the DAPM performance improvements we've been marking all widgets
as not dirty after each DAPM run. Since _PRE and _POST events aren't part
of the DAPM graph this has rendered them non-functional, they will never be
marked dirty again and thus will never be run again.

Fix this by skipping them when marking widgets as not dirty.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Cc: stable@vger.kernel.org

sound/soc/soc-dapm.c

@@ -1598,7 +1598,15 @@ static int dapm_power_widgets(struct snd_soc_dapm_context *dapm, int event)
 	}
 
 	list_for_each_entry(w, &card->widgets, list) {
-		list_del_init(&w->dirty);
+		switch (w->id) {
+		case snd_soc_dapm_pre:
+		case snd_soc_dapm_post:
+			/* These widgets always need to be powered */
+			break;
+		default:
+			list_del_init(&w->dirty);
+			break;
+		}
 
 		if (w->power) {
 			d = w->dapm;