x86: VMX: Add a VMX-preemption timer expiration test

When the VMX-preemption timer is activated, code executing in VMX
non-root operation should never be able to record a TSC value beyond
the deadline imposed by adding the scaled VMX-preemption timer value
to the first TSC value observed by the guest after VM-entry.

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Message-Id: <20200508203938.88508-1-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>