target/riscv: Add max32 CPU for RV64 QEMU

target/riscv: Add max32 CPU for RV64 QEMU

We may need 32-bit max for RV64 QEMU. Thus we add these two CPUs
for RV64 QEMU.

The reason we don't expose them to RV32 QEMU is that we already have
max cpu with the same configuration. Another reason is that we want
to follow the RISC-V custom where addw instruction doesn't exist in
RV32 CPU.

Signed-off-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Suggested-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20240919055048.562-8-zhiwei_liu@linux.alibaba.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>