ASoC: rt5640: add supplys for dac power

The DAC1/2 power is for both DACs and related mixer/mux. Add SUPPLY
type widgets to support it.

Signed-off-by: Jack Yu <jack.yu@realtek.com>
Signed-off-by: Bard Liao <bardliao@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>