ASoC: dapm: Ignore isolated signal generators for power purposes

A signal generator has no power control itself and so shouldn't cause a
power up of the device.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/soc-dapm.c

@@ -1435,9 +1435,13 @@ static int dapm_power_widgets(struct snd_soc_dapm_context *dapm, int event)
 			/* Supplies and micbiases only bring the
 			 * context up to STANDBY as unless something
 			 * else is active and passing audio they
-			 * generally don't require full power.
+			 * generally don't require full power.  Signal
+			 * generators are virtual pins and have no
+			 * power impact themselves.
 			 */
 			switch (w->id) {
+			case snd_soc_dapm_siggen:
+				break;
 			case snd_soc_dapm_supply:
 			case snd_soc_dapm_regulator_supply:
 			case snd_soc_dapm_micbias: