[PowerPC] Support register name prefixes for vector registers

Match binutils by supporting the optional register name prefix for new vector
registers ("vs" for VSX registers and "q" for QPX registers).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235665 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed