ASoC: tegra: support a Mic Jack in the Tegra+RT5640 machine driver

Add a Mic Jack widget to the Tegra+RT5640 machine driver, and document
this in the DT binding. This enables the DT to include the Mic Jack in
the audio routing table, and hence enables capture of audio, in addition
to the previously-working playback.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/sound/nvidia,tegra-audio-rt5640.txt

@@ -16,6 +16,7 @@ Required properties:
 
   * Headphones
   * Speakers
+  * Mic Jack
 
 - nvidia,i2s-controller : The phandle of the Tegra I2S controller that's
   connected to the CODEC.

sound/soc/tegra/tegra_rt5640.c

@@ -99,6 +99,7 @@ static struct snd_soc_jack_gpio tegra_rt5640_hp_jack_gpio = {
 static const struct snd_soc_dapm_widget tegra_rt5640_dapm_widgets[] = {
 	SND_SOC_DAPM_HP("Headphones", NULL),
 	SND_SOC_DAPM_SPK("Speakers", NULL),
+	SND_SOC_DAPM_MIC("Mic Jack", NULL),
 };
 
 static const struct snd_kcontrol_new tegra_rt5640_controls[] = {