ASoC: da7210: Add support for line input and mic

DA7210 has three line inputs (AUX1 Left, AUX1 Right and AUX2) and
a stereo MIC. This patch adds gain controls for MIC, AUX1, AUX2 as
well as INPGA.

Signed-off-by: Ashish Chavan <ashish.chavan@kpitcummins.com>
Signed-off-by: David Dajun Chen <dchen@diasemi.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>