Drop support for dematerializing.

It was only used on lib/Linker and the use was "dead" since it was used on a
function the IRMover had just moved.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256019 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed