[U-Boot] Bring tinker-rk3288 back into SPL size limit?

Hey,

With Heinrich's series to enforce a size limit on SPL and Simon Goldschmidt's enhancements on top of that, we're now seeing that tinker-rk3288 has an SPL that is too large to function. And it's now also causing the build to fail. So, good that we're catching this at least. Can you please look into what we need to do to get the image to fit within the size constraints? Thanks!