ppc/xics: Fix stale irq->status bits after get

ics_get_kvm_state() "or"s set bits into irq->status but does not mask
out clear bits.

Correct this by initializing the IRQ status to zero before adding bits
to it.

Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/intc/xics_kvm.c

@@ -213,6 +213,7 @@ static void ics_get_kvm_state(ICSState *ics)
             irq->priority = irq->saved_priority;
         }
 
+        irq->status = 0;
         if (state & KVM_XICS_PENDING) {
             if (state & KVM_XICS_LEVEL_SENSITIVE) {
                 irq->status |= XICS_STATUS_ASSERTED;