[PowerPC] Mark sanitizer test case unsupported for powerpc64

The author of "https://reviews.llvm.org/D92428" marked
'resize_tls_dynamic.cpp' with XFAIL for powerpc64 since
it fails on a bunch of PowerPC buildbots. However, the
original test case passes on clang-ppc64le-rhel bot. So
marking this as XFAIL makes this bot to fail as the test
case passes unexpectedly. We are marking this unsupported
on all PowerPC64 for now until it is fixed for all the
PowerPC buildbots.