[PowerPC] Pretty-print CR bits the way the binutils disassembler does

[PowerPC] Pretty-print CR bits the way the binutils disassembler does

This patch just adds printing of CR bit registers in a more human-readable
form akin to that used by the GNU binutils.

Differential Revision: https://reviews.llvm.org/D31494

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309001 91177308-0d34-0410-b5e6-96231b3b80d8