asoc: codecs: Fix volume fluctuation issue in headphone playback

HPH PA pull down control is set to force ON instead of auto
due of which saturation/noise is observed in headset
playback at highest volumes. Set pull down control
to Auto to fix this issue.

Change-Id: I465588f46b04bbb32d84f76b8b5bedd2ef21bd2a
Signed-off-by: Aditya Bavanari <abavanar@codeaurora.org>