[FHI72] Fix the PRACH FFT size ru_config->fftSize is used for the C-plane Section Type 3 which is dedicated for PRACH and mixed numerology. Previously, we assumed that PRACH FFT size is equivalent to PxSCH FFT size, but should be based on the PRACH format. Tests with the following RUs: - [x] Benetel v1.2.2 & v1.4.1 - [x] VVDN Gen 3 - [x] Liteon 02.00.10 - [x] Metanoia v2.2.8 (Jura)