ASoC: mediatek: rework clock functions for MT2701

Reworks clock part to make it more reasonable. The current changes are:

- Replace regmap operations by CCF APIs. Doing so, we just need to handle
  the element clocks and can also get accurate information via CCF.

- Rename clocks to make them more generic so that the future revisions
  of the IP can adapt gracefully.

- Regroup 'aud_clks[]' by usage - the basic needs and I2S parts:

  The new code just keep the common clocks in array and let SoC self decide
  I2S numbers - If future chips have different sets of channels we will
  add a little more abstract here.

  Moreover, this patch moves I2S clocks to the struct mt2701_i2s_data
  so that we can easily manage them when calls .prepare() and .shutdown().

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Tested-by: Garlic Tseng <garlic.tseng@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>