[RISCV] Add TT-Ascalon-d8 processor (#115100)
Ascalon is an out-of-order CPU core from Tenstorrent. Overview:
https://tenstorrent.com/ip/tt-ascalon
Adding 8-wide version, -mcpu=tt-ascalon-d8. Scheduling model will be
added in a separate PR.
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Co-authored-by: Anton Blanchard <antonb@tenstorrent.com>
