ASoC: Disable microphone input for AT91SAM9G20-EK by default

As shipped the board does not have inputs but it is relatively
straightforward to modify the board to hook them up so support
is provided in the driver. When these modifications have not
been made enabling the microphone stage can cause problems.

Add an ifdef to disable this by default. Don't put it into
Kconfig since users will have to get their soldering irons
out to change things.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/atmel/sam9g20_wm8731.c

@@ -56,6 +56,13 @@
 
 #define MCLK_RATE 12000000
 
+/*
+ * As shipped the board does not have inputs.  However, it is relatively
+ * straightforward to modify the board to hook them up so support is left
+ * in the driver.
+ */
+#undef ENABLE_MIC_INPUT
+
 static struct clk *mclk;
 
 static int at91sam9g20ek_startup(struct snd_pcm_substream *substream)
@@ -170,8 +177,13 @@ static int at91sam9g20ek_wm8731_init(struct snd_soc_codec *codec)
 	snd_soc_dapm_nc_pin(codec, "RLINEIN");
 	snd_soc_dapm_nc_pin(codec, "LLINEIN");
 
-	/* always connected */
+#ifdef ENABLE_MIC_INPUT
 	snd_soc_dapm_enable_pin(codec, "Int Mic");
+#else
+	snd_soc_dapm_nc_pin(codec, "Int Mic");
+#endif
+
+	/* always connected */
 	snd_soc_dapm_enable_pin(codec, "Ext Spk");
 
 	snd_soc_dapm_sync(codec);