ASoC: dmic: add Kconfig prompt for the generic dmic codec.

Add Kconfig prompt for the generic digital mic to make it configurable
through menuconfig
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/Kconfig

@@ -578,7 +578,11 @@ config SND_SOC_DA9055
 	tristate
 
 config SND_SOC_DMIC
-	tristate
+	tristate "Generic Digital Microphone CODEC"
+	depends on GPIOLIB
+	help
+	  Enable support for the Generic Digital Microphone CODEC.
+	  Select this if your sound card has DMICs.
 
 config SND_SOC_HDMI_CODEC
 	tristate