lnDSO: Pics of HW modification to use a GD32VF103 (RISCV)

 For reference, here are the modifications to do to replace the STM32F103 (or CH32F103 on some cheap clones) by a GD32VF103



There are 2 extra modifications, unrelated to the VF103 : 

* Put a schottky in reverse between r36 and ground to clamp the negative voltage. Probably not needed, but i saw -4 v when testing there.

* Replace the diode on the bottom right by a P Mosfet in reverse to avoid wasting 0.6 v there (SH1B). 

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