XFAIL the test cases for r186044 on Hexagon

For some reason, the Hexagon backend does not reject these invalid static
initializer expressions, but instead crashes in AsmPrinter::EmitGlobalConstant.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186045 91177308-0d34-0410-b5e6-96231b3b80d8