target/riscv/csr.c: use env_archcpu() in ctr()

target/riscv/csr.c: use env_archcpu() in ctr()

We don't need to use env_cpu() and CPUState().

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20230224174520.92490-2-dbarboza@ventanamicro.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>