target/riscv: introduce riscv_cpu_cfg()

target/riscv: introduce riscv_cpu_cfg()

We're going to do changes that requires accessing the RISCVCPUConfig
struct from the RISCVCPU, having access only to a CPURISCVState 'env'
pointer. Add a helper to make the code easier to read.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20230222185205.355361-2-dbarboza@ventanamicro.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>