ASoC: twl6040: Workaround for headset DC offset caused pop noise

Both Headset DAC need to be turned on/off at the same time before
any of the output drivers are enabled (HS Left/Right, Earpiece).
Move the HS DAC enable code to sequenced DAPM_SUPPLY, and attach
it to the DACs.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>