mod_risc_v.rs should not expose the EPPB block

[adfernandes]

On RISC-V accessing the EPBB block will trigger a bus fault, so mod_risc_v.rs should not expose that peripheral.

I will try my hand at modifying svd/RP2350.yaml to patch as appropriate, but don't know svdtool well enough to know if it supports conditional patching... this might need a slightly more invasive patch.

Suggestions are welcome, I'm happy to do the work and test!