[PowerPC] Add initialization for some ppc passes

Summary:

Some llc debug options need pass-name as the parameters.
But if we use the pass-name ppc-early-ret, we will get below error:
llc test.ll -stop-after ppc-early-ret
LLVM ERROR: "ppc-early-ret" pass is not registered.
Below pass-names have the pass is not registered error:
ppc-ctr-loops
ppc-ctr-loops-verify
ppc-loop-preinc-prep
ppc-toc-reg-deps
ppc-vsx-copy
ppc-early-ret
ppc-vsx-fma-mutate
ppc-vsx-swaps
ppc-reduce-cr-ops
ppc-qpx-load-splat
ppc-branch-coalescing
ppc-branch-select

Reviewed By: jsji

Differential Revision: https://reviews.llvm.org/D60248

llvm-svn: 358256