Request firmware for TH1520's BXM-4-64 GPU.

TH1520 is a RISC-V SoC equipped with BXM-4-64 (BVNC 36.52.104.182) MC1 GPU.

P.S. If possible, could you supply device_info of Mesa too in dev/devinfo branch? Although I expect it to be similar to BXE-4-32 and BXS-4-64 (maybe more similar to the former).