[tests] Move new tests into the PowerPC folder

That way they get marked as UNSUPPORTED by LIT when the ppc backend has not
been built.

diff --git a/llvm/test/CodeGen/builtins-ppc-xlcompat-move-tofrom-regs.ll b/llvm/test/CodeGen/PowerPC/builtins-ppc-xlcompat-move-tofrom-regs.ll
similarity index 100%
rename from llvm/test/CodeGen/builtins-ppc-xlcompat-move-tofrom-regs.ll
rename to llvm/test/CodeGen/PowerPC/builtins-ppc-xlcompat-move-tofrom-regs.ll

diff --git a/llvm/test/CodeGen/builtins-ppc-xlcompat-prefetch.ll b/llvm/test/CodeGen/PowerPC/builtins-ppc-xlcompat-prefetch.ll
similarity index 100%
rename from llvm/test/CodeGen/builtins-ppc-xlcompat-prefetch.ll
rename to llvm/test/CodeGen/PowerPC/builtins-ppc-xlcompat-prefetch.ll