Pointer variables clean up for ivas_quantise_real_values() and ivas_deindex_real_index()

These functions were originally written to quantize/unquantize two dimensional arrays but currently they are being used to quantize either one variable at a time OR one dimensional arrays. Given that the function still expects two dimensional arrays, there is unnecessary code to convert single dimension to double dimension every time these functions are called. This adds dirty pointer tricks in the code which needs to be cleaned up.