ASoC: rt5677: Use specific r/w function for DSP mode

In DSP mode, the register r/w should use the specific function to access
that is invoked by address mapping of the DSP.

The MX-65[1] is for switching DSP or codec mode.

Signed-off-by: Oder Chiou <oder_chiou@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>