Followup to 03039ab2ee.
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=58335
If I observed it right we currently leave `init_xstate_features` on older computers with EnabledFeatures being zero. This leads in `__wine_syscall_dispatcher` to getting the xsave64 getting called with "$rax = 0x0", therefore e.g. xmm6 gets not saved to the stack. But later e.g. xmm6 gets restored from stack in `__wine_syscall_dispatcher` (see [__wine_syscall_dispatcher](https://gitlab.winehq.org/wine/wine/-/blob/wine-10.12/dlls/ntdll/unix/signal...))
-- v2: ntdll/tests: Allow non-AVX CPUs in XState feature tests.