Fix typo cgroupDriver -> cgroup-driver

Signed-off-by: Xin Wang <[email protected]>

Author: Xin Wang

cmd/kubeadm/app/apis/kubeadm/v1beta1/doc.go

@@ -180,7 +180,7 @@ limitations under the License.
 // 	    value: "master"
 // 	    effect: "NoSchedule"
 // 	  kubeletExtraArgs:
-// 	    cgroupDriver: "cgroupfs"
+// 	    cgroup-driver: "cgroupfs"
 // 	localAPIEndpoint:
 // 	  advertiseAddress: "10.100.0.1"
 // 	  bindPort: 6443