Remove some more unused headers from MachineFunction.h and friends.

Most of these headers are still included via transitive includes and
so won't likely show any problems or improvements in incremental
rebuild time.

Differential Revision: https://reviews.llvm.org/D60741

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358468 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed