ASoC: mediatek: add sub dai to mtk_base_afe

In MediaTek SoC chip we have multiple DAI,
such as I2S, ADDA, PCM, etc.

Organize each DAI in to one sub dai,
with its dai driver, controls, widgets, routes.

add mtk_afe_combine_sub_dai() to combine
dai driver from each DAI.

add mtk_afe_add_sub_dai_control() to register
the control, widget, routes to component.

Signed-off-by: KaiChieh Chuang <kaichieh.chuang@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>