Revert "SMP: Calculate LTK on BR SMP begin"

Bug: 232409640
Tag: #refactor
Test: gd/cert/run

This reverts commit c73e0297.

Reason for revert: Reverting this fixes b/232409640 where we are sending
signing information to the carkit twice

Change-Id: I296d0fe642d91088ea90dbda24e82f9044ad5ba0