ASoC: wcd9xxx: Register callback for external micbias

Even if external micbias is used for recording, callback
needs to be registered to setup for recording. Register
same callback as used with internal micbias.

CRs-Fixed: 550513
Change-Id: If7f606f265d46aa20a29fc97afd2468e7fe97379
Signed-off-by: Simmi Pateriya <simmip@codeaurora.org>