Temporarily revert "[PowerPC] Allow tail calls of fastcc functions from C CallingConv functions."

It is causing sanitizer failures on llvm tests in a bootstrapped compiler. No bot link since it's currently down, but following up to get the bot up.

This reverts commit r319218.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320106 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed