target/riscv: add Ventana's Veyron V1 CPU

target/riscv: add Ventana's Veyron V1 CPU

Add a virtual CPU for Ventana's first CPU named veyron-v1. It runs
exclusively for the rv64 target. It's tested with the 'virt' board.

CPU specs and general information can be found here:

https://www.nextplatform.com/2023/02/02/the-first-risc-v-shot-across-the-datacenter-bow/

Signed-off-by: Rahul Pathak <rpathak@ventanamicro.com>
Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230418123624.16414-1-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>