ASoC: tegra: Add sink for the internal mic to tegra_max98090

Also adds a control for the pin of the internal mic, so userspace can
apply policy when the state of the external mic jack changes.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>