Revert r223049, r223050 and r223051 while investigating test failures.

I didn't foresee affecting the Clang test suite :/

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223054 91177308-0d34-0410-b5e6-96231b3b80d8
ARM: lower tail calls correctly when using GHC calling convention.

Patch by Ben Gamari.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223055 91177308-0d34-0410-b5e6-96231b3b80d8