diag: dci: Initialize diag dci channels correctly

Diag driver initializes the DCI channel workqueues after
registering with SMD. In some cases, the driver can be notified
of channel open before the intialization is complete. This path
initializes the DCI channel workqueues before registering with
SMD.

Change-Id: I93c74a14e5aff0b9eadc2bff3da859fc4aa49891
Signed-off-by: Ravi Aravamudhan <aravamud@codeaurora.org>