Patch series for 4.19 to compile powerpc with Clang

Hi Greg and Sasha,

Attached is an mbox with a series of patches to allow building the powerpc kernel with Clang. We have been running continuous integration that builds and boots the kernel in QEMU for almost two months now with no regressions. This is on top of 4.19.14, there should be no conflicts but let me know if I messed something up.

I will send a series for 4.14 in a little bit as well.

Thank you, Nathan