target/riscv: Adjust vsetvl according to XLEN

Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20220120122050.41546-17-zhiwei_liu@c-sky.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.h

@@ -491,6 +491,11 @@ static inline RISCVMXL cpu_recompute_xl(CPURISCVState *env)
 }
 #endif
 
+static inline int riscv_cpu_xlen(CPURISCVState *env)
+{
+    return 16 << env->xl;
+}
+
 /*
  * Encode LMUL to lmul as follows:
  *     LMUL    vlmul    lmul