[PowerPC] Add a full condition code register to make the "cc" clobber work

gcc inline asm supports specifying "cc" as a clobber of all condition
registers. Add just enough modeling of the full register to make this work.
Fixed PR19326.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205630 91177308-0d34-0410-b5e6-96231b3b80d8