[clang] [llvm] [RISCV] Add Hazard3 CPU (PR #102452)

[Alex Bradbury via cfe-commits]

asb wrote:

I think our conclusion from the sync-up call discussion matches what we'd roughly concluded in this thread, which is that with an instantiation of Hazard3 shipping in the RP2350 this isn't really a good test case for questions about when it's worth including a CPU definition for an open source core.

So for this particular PR, we just need a name people are happy with (perhaps check if the vendor has a preference?). Something like `-mcpu=rp2350-hazard3` perhaps?

https://github.com/llvm/llvm-project/pull/102452