asoc: wcd937x: set default power level as ULP for wcd937x headphones

For headphone playback, update default power level
to Ultra_Low_Power(ULP) on wcd9370.

Change-Id: Ic5e76d8f8fca1806780a4dbc679166a68c31edf3
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>