ASoC: da732x: Fix control-less DAPM routes

Routes without a control must use NULL for the control name. The da732x
driver uses "NULL" instead in a few places. Previous to commit 5fe5b767dc
("ASoC: dapm: Do not pretend to support controls for non mixer/mux widgets")
the DAPM core silently ignored non-NULL controls on non-mixer and non-mux
routes. But starting with that commit it will complain and not add the
route breaking the da732x driver in the process.

This patch replaces the incorrect "NULL" control name with NULL to fix the
issue.

Fixes: 5fe5b767dc ("ASoC: dapm: Do not pretend to support controls for non mixer/mux widgets")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

sound/soc/codecs/da732x.c

@@ -876,11 +876,11 @@ static const struct snd_soc_dapm_widget da732x_dapm_widgets[] = {
 
 static const struct snd_soc_dapm_route da732x_dapm_routes[] = {
 	/* Inputs */
-	{"AUX1L PGA", "NULL", "AUX1L"},
-	{"AUX1R PGA", "NULL", "AUX1R"},
+	{"AUX1L PGA", NULL, "AUX1L"},
+	{"AUX1R PGA", NULL, "AUX1R"},
 	{"MIC1 PGA", NULL, "MIC1"},
-	{"MIC2 PGA", "NULL", "MIC2"},
-	{"MIC3 PGA", "NULL", "MIC3"},
+	{"MIC2 PGA", NULL, "MIC2"},
+	{"MIC3 PGA", NULL, "MIC3"},
 
 	/* Capture Path */
 	{"ADC1 Left MUX", "MIC1", "MIC1 PGA"},