nvdimm: fix memory leak in error code path

object_get_canonical_path_component() returns a heap-allocated string
that must be freed using g_free().

Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/mem/nvdimm.c

@@ -98,6 +98,7 @@ static void nvdimm_realize(PCDIMMDevice *dimm, Error **errp)
                    "small to contain nvdimm label (0x%" PRIx64 ") and "
                    "aligned PMEM (0x%" PRIx64 ")",
                    path, memory_region_size(mr), nvdimm->label_size, align);
+        g_free(path);
         return;
     }