ASoC: wcd9320: Prevent calling PA event unnecessarily during ANC

When Headphone ANC is enabled, do not call the headphone PA event
in pre-power down case, only in post-power down.
Headphone PA event will only process this call in post-power
down case.

Change-Id: Icc66f46977be08a55aca2e8c74ef6a828b463baf
Signed-off-by: Damir Didjusto <damird@codeaurora.org>