hw/net/vhost_net: Silence compiler warning when compiling with -Wshadow

Rename the innermost local variables to avoid compiler warnings
with "-Wshadow".

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20231004084939.96349-1-thuth@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

hw/net/vhost_net.c

@@ -313,8 +313,8 @@ fail:
                 /* Queue might not be ready for start */
                 continue;
             }
-            int r = vhost_net_set_backend(&net->dev, &file);
-            assert(r >= 0);
+            int ret = vhost_net_set_backend(&net->dev, &file);
+            assert(ret >= 0);
         }
     }
     if (net->nc->info->poll) {
@@ -629,8 +629,8 @@ err_start:
     if (net->nc->info->type == NET_CLIENT_DRIVER_TAP) {
         file.fd = VHOST_FILE_UNBIND;
         file.index = idx;
-        int r = vhost_net_set_backend(&net->dev, &file);
-        assert(r >= 0);
+        int ret = vhost_net_set_backend(&net->dev, &file);
+        assert(ret >= 0);
     }
 
     vhost_dev_stop(&net->dev, vdev, false);