On napier AX, HK2.0 ast search is tied to lmac_id.
This ast search feature is added to support DBDC repeater usecase.
Assign lmac id 3 to search by default on all macs until more
formal per pdev changes are made. This enables 2g.
Change-Id: Ia06d9243bddd3f4943426d6b0de3f452a252d819
CRs-fixed: 2198431