ASoC: dapm: allow muxes to force a disconnect

Let soc_dapm_mux_update_power() accept NULL as 'e' enum.

It makes the code a bit more robust and, more importantly, let the calling
mux force a disconnect of the output path if necessary.

This is useful if the dapm elements following the mux must be off
while updating the mux, to avoid glitches or force a (re)configuration.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-dapm.c

@@ -2245,7 +2245,7 @@ static int soc_dapm_mux_update_power(struct snd_soc_card *card,
 	dapm_kcontrol_for_each_path(path, kcontrol) {
 		found = 1;
 		/* we now need to match the string in the enum to the path */
-		if (!(strcmp(path->name, e->texts[mux])))
+		if (e && !(strcmp(path->name, e->texts[mux])))
 			connect = true;
 		else
 			connect = false;