KVM: selftests: do not substitute SVM/VMX check with KVM_CAP_NESTED_STATE check

state_test/smm_test use KVM_CAP_NESTED_STATE check as an indicator for
nested VMX/SVM presence and this is incorrect. Check for the required
features dirrectly.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200610135847.754289-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>