ASoC: uniphier: evea: add switch for changing source of line-in

This patch adds mixer switch for changing audio source of line-in.
We can choose one of LIN1, 2, 3, default is LIN1.

Signed-off-by: Katsuhiro Suzuki <suzuki.katsuhiro@socionext.com>
Signed-off-by: Mark Brown <broonie@kernel.org>