Revert "SMP: Calculate LTK on BR SMP begin"

This reverts commit c73e0297.

Bug: 232409640
Tag: #refactor
Test: gd/cert/run
Ignore-AOSP-First: T bugfix

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

Merged-In: I296d0fe642d91088ea90dbda24e82f9044ad5ba0
Change-Id: I3f71c0df843a1f1bc671dbc89d25a223de22c497