emulators/qemu: fix build on powerpc*

../util/cpuinfo-ppc.c:49:18: error: use of undeclared identifier 'PPC_FEATURE2_ISEL'

if (hwcap2 & PPC_FEATURE2_ISEL) {
             ^

../util/cpuinfo-ppc.c:62:26: error: use of undeclared identifier 'PPC_FEATURE2_VEC_CRYPTO'

if (hwcap2 & PPC_FEATURE2_VEC_CRYPTO) {
             ^

2 errors generated.