Remove BTA_DM_LINK_POLICY_SETTINGS & friends

it's essentially a constant, set to a variable which never changes

and it's only used once

inline it

q.e.d.

Bug: 159815595
Tag: #refactor
Test: compile & verify basic functions working
Change-Id: Icd4f61ae6c7eb36894808f5ee3b5514d95131fc7