target/riscv: Add BOSC's Xiangshan Kunminghu CPU

Add a CPU entry for the Xiangshan Kunminghu CPU, an open-source,
high-performance RISC-V processor. More details can be found at:
https://github.com/OpenXiangShan/XiangShan

Note: The ISA extensions supported by the Xiangshan Kunminghu CPU are
categorized based on four RISC-V specifications: Volume I: Unprivileged
Architecture, Volume II: Privileged Architecture, AIA, and RVA23. The
extensions within each category are organized according to the chapter
order in the specifications.

Signed-off-by: Yu Hu <huyu@bosc.ac.cn>
Signed-off-by: Ran Wang <wangran@bosc.ac.cn>
Signed-off-by: Borong Huang <3543977024@qq.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250425122212.364-1-wangran@bosc.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
2 files changed