kvm: vmx: add cpu into VMX preemption timer bug list

This patch adds Intel "Xeon CPU E3-1220 V2", with CPUID.01H.EAX=0x000306A8,
into the list of known broken CPUs which fail to support VMX preemption
timer. This bug was found while running the APIC timer test of
kvm-unit-test on this specific CPU, even though the errata info can't be
located in the public domain for this CPU.
Signed-off-by: Wei Huang <wei@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -469,6 +469,8 @@ static u32 vmx_preemption_cpu_tfms[] = {
  /* 321324.pdf - AAK139 - D0 - Xeon 5500 */
  /* 320836.pdf - AAJ124 - D0 - i7-900 Extreme and i7-900 Desktop */
 0x000106A5,
+ /* Xeon E3-1220 V2 */
+0x000306A8,
 };
 
 static inline bool cpu_has_broken_vmx_preemption_timer(void)