ASoC: rt5645: Add codec driver

This patch adds the Realtek ALC5645 codec driver. It is the base
version that because the jack detect function is not implemented to
it, the headphone and AMIC1 are not workable. We will fill up the
further functions later.

Signed-off-by: Bard Liao <bardliao@realtek.com>
Signed-off-by: Oder Chiou <oder_chiou@realtek.com>
Signed-off-by: Mark Brown <broonie@linaro.org>