Spectral scan for QCA6018 failed due decoding the FFT bin in 2 bytes.
HWS team confirmed that for QCA6018, the FFT bin is in 4 bytes
representation.
Fixing this by modify the fftbin size WAR for QCA6018 to decode
4 bytes FFT bins.
Change-Id: I60e07370f7191544269d52640ae072f2a41f3833
CRs-Fixed: 2487055