kvm: fix error message when failing to unregister slot

"overlapping" is a leftover, let's drop it.
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20171016144302.24284-5-david@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

accel/kvm/kvm-all.c

@@ -734,7 +734,7 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
         mem->memory_size = 0;
         err = kvm_set_user_memory_region(kml, mem);
         if (err) {
-            fprintf(stderr, "%s: error unregistering overlapping slot: %s\n",
+            fprintf(stderr, "%s: error unregistering slot: %s\n",
                     __func__, strerror(-err));
             abort();
         }