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>

target/riscv/csr.c

@@ -108,8 +108,7 @@ static RISCVException vs(CPURISCVState *env, int csrno)
 static RISCVException ctr(CPURISCVState *env, int csrno)
 {
 #if !defined(CONFIG_USER_ONLY)
-    CPUState *cs = env_cpu(env);
-    RISCVCPU *cpu = RISCV_CPU(cs);
+    RISCVCPU *cpu = env_archcpu(env);
     int ctr_index;
     target_ulong ctr_mask;
     int base_csrno = CSR_CYCLE;