ASoC: rt5640: Fix NULL dereference on module unload

The rt5640->jack is NULL if jack is already disabled at the time of
driver's module unloading.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20200106014707.11378-1-digetx@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt5640.c

@@ -2432,6 +2432,13 @@ static void rt5640_disable_jack_detect(struct snd_soc_component *component)
 {
 	struct rt5640_priv *rt5640 = snd_soc_component_get_drvdata(component);
 
+	/*
+	 * soc_remove_component() force-disables jack and thus rt5640->jack
+	 * could be NULL at the time of driver's module unloading.
+	 */
+	if (!rt5640->jack)
+		return;
+
 	disable_irq(rt5640->irq);
 	rt5640_cancel_work(rt5640);