ASoC: wcd_cpe_services: delete the redundant worker thread

Currently worker thread in cpe service is created twice.
The second thread handler overwrites the first one. The first
thread is not freed  when the service is cleaned up. The fix
prevents creation of the redundant thread.

CRs-Fixed: 949165
Change-Id: Idd76b76d4f7f25d2592ca7c336dbee77b6efc7eb
Signed-off-by: Walter Yang <yandongy@codeaurora.org>