KVM: selftests: Use this_cpu_has() in CR4/CPUID sync test

Use this_cpu_has() to query OSXSAVE from the L1 guest in the CR4=>CPUID
sync test.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220614200707.3315957-34-seanjc@google.com