PatchSelect works only for 2D data

[paskino]

The PATCHSEL_CPU function only works for 2D data, although a function for 3D seems to be implemented in the C library.

https://github.com/vais-ral/CCPi-Regularisation-Toolkit/blob/71f8d304d804b54d378f0ed05539f01aaaf13758/src/Python/src/cpu_regularisers.pyx#L608-L612