KVM: selftests: update hyperv_cpuid with SynDBG tests

Update tests to reflect new CPUID capabilities with SYNDBG.
Check that we get the right number of entries and that
0x40000000.EAX always returns the correct max leaf.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Jon Doron <arilou@gmail.com>
Message-Id: <20200529134543.1127440-7-arilou@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>