Add wildcard toleration to nvidia-gpu-device-plugin.

This addon runs only on nodes with GPUs and it's essential for their
proper function.

cluster/addons/device-plugins/nvidia-gpu/daemonset.yaml

@@ -23,9 +23,10 @@ spec:
               - key: cloud.google.com/gke-accelerator
                 operator: Exists
       tolerations:
-      - key: "nvidia.com/gpu"
+      - operator: "Exists"
+        effect: "NoExecute"
+      - operator: "Exists"
         effect: "NoSchedule"
-        operator: "Exists"
       hostNetwork: true
       hostPID: true
       volumes: