valgrind/i386: avoid false positives on KVM_SET_PIT ioctl

struct kvm_pit_state2 contains pad fields. Let's use a designated
initializer to avoid false positives from valgrind/memcheck.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/i386/kvm/i8254.c

@@ -138,7 +138,7 @@ static void kvm_pit_get(PITCommonState *pit)
 static void kvm_pit_put(PITCommonState *pit)
 {
     KVMPITState *s = KVM_PIT(pit);
-    struct kvm_pit_state2 kpit;
+    struct kvm_pit_state2 kpit = {};
     struct kvm_pit_channel_state *kchan;
     struct PITChannelState *sc;
     int i, ret;