valgrind: avoid false positives in KVM_GET_DIRTY_LOG ioctl

struct kvm_dirty_log contains padding fields that trigger false
positives in valgrind. 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>

kvm-all.c

@@ -417,7 +417,7 @@ static int kvm_physical_sync_dirty_bitmap(MemoryRegionSection *section)
 {
     KVMState *s = kvm_state;
     unsigned long size, allocated_size = 0;
-    KVMDirtyLog d;
+    KVMDirtyLog d = {};
     KVMSlot *mem;
     int ret = 0;
     hwaddr start_addr = section->offset_within_address_space;