Looks like it should just be something like this:
CL cl = CLPlatform.getLowLevelCLInterface();
...
cl.clSetKernelArg(kernel, 3, bytes, null);
You can look in
https://github.com/JogAmp/jocl/blob/master/test/com/jogamp/opencl/LowLevelBindingTest.java for an example of clSetKernelArg().