drivers/net/hyperv/netvsc.c: remove unnecessary null test before kfree

Fix checkpatch warning:
WARNING: kfree(NULL) is safe this check is probably not required

Cc: Haiyang Zhang <[e-mail]>
Cc: [e-mail]
Signed-off-by: Fabian Frederick <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/hyperv/netvsc.c

···
 	vmbus_close(device->channel);
 
 cleanup:
-
-	if (net_device)
-		kfree(net_device);
+	kfree(net_device);
 
 	return ret;
 }