[PowerPC] On PPC32, 128-bit shifts might be runtime calls

The counter-loops formation pass needs to know what operations might be
function calls (because they can't appear in counter-based loops). On PPC32,
128-bit shifts might be runtime calls (even though you can't use __int128 on
PPC32, it seems that SROA might form them).

Fixes PR19709.

llvm-svn: 208501