ASoC: max98090: Use SOC_ENUM_SINGLE_VIRT_DECL()

For the upcoming consolidation for MUXs and virtual MUXs we need to mark virtual
enums as such.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/codecs/max98090.c

@@ -871,7 +871,7 @@ static const struct snd_kcontrol_new max98090_mic2_mux =
 
 static const char *dmic_mux_text[] = { "ADC", "DMIC" };
 
-static SOC_ENUM_SINGLE_EXT_DECL(dmic_mux_enum, dmic_mux_text);
+static SOC_ENUM_SINGLE_VIRT_DECL(dmic_mux_enum, dmic_mux_text);
 
 static const struct snd_kcontrol_new max98090_dmic_mux =
 	SOC_DAPM_ENUM_VIRT("DMIC Mux", dmic_mux_enum);