ASoC: bg: Ensure to hanlde pm events only after codec probe done

Audio codec needs to handle pm events only after codec probe done.
So register Audio to pm service only after after codec probe done.

Change-Id: I36ad6a86d5342995946d20979974af0b4f60170a
Signed-off-by: Bala Kishore Pati <balakishorepati@codeaurora.org>