[PowerPC] Add support for vector bool __int128 for Power10

Summary:
This patch adds support for `vector bool __int128` type for Power10.

Reviewers: #powerpc, hfinkel, lei, stefanp, amyk

Reviewed By: #powerpc, lei, amyk

Subscribers: lei, amyk, wuzish, nemanjai, shchenz, cfe-commits

Tags: #llvm, #powerpc, #clang

Differential Revision: https://reviews.llvm.org/D81816