[PowerPC] Refactor popcnt[dw] target features

Instead of using two feature bits, one to indicate the availability of the
popcnt[dw] instructions, and another to indicate whether or not they're fast,
use a single enum. This allows more consistent control via target attribute
strings, and via Clang's command line.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264690 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed