bta_dm_check_av(BTA_DM_API_SEARCH_EVT) will never return true

BTA_DM_API_SEARCH_EVT blocks role switch, so it will always return
false.
also, does not have any side effects

this code will never be invoked.

Bug: 159815595
Tag: #refactor
Test: compile & verify basic functions working
Change-Id: Iceebe8678d581512b9bc00119a63abbd98b483c1