[PPCGCodeGen] Change printf to outs() to prevent garbled output. [NFC]

Summary:
It appears that llvm uses unbuffered C++ streams. So, we should not
mix C and C++ stream operations, because that will give us mixed
up output.

Reviewers: efriedma, jdoerfert, Meinersbur, gareevroman, sebpop, zinob, huihuiz, pollydev, grosser, singam-sanjay, philip.pfaffe

Reviewed By: philip.pfaffe

Subscribers: nemanjai, kbarton

Differential Revision: https://reviews.llvm.org/D40126

llvm-svn: 336288