target/riscv/csr.c: use 'vlenb' instead of 'vlen'

As a bonus, we're being more idiomatic using cpu->cfg.vlenb when
reading CSR_VLENB.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240122161107.26737-3-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/csr.c

@@ -683,7 +683,7 @@ static RISCVException read_vl(CPURISCVState *env, int csrno,
 
 static int read_vlenb(CPURISCVState *env, int csrno, target_ulong *val)
 {
-    *val = riscv_cpu_cfg(env)->vlen >> 3;
+    *val = riscv_cpu_cfg(env)->vlenb;
     return RISCV_EXCP_NONE;
 }
 
@@ -738,7 +738,7 @@ static RISCVException write_vstart(CPURISCVState *env, int csrno,
      * The vstart CSR is defined to have only enough writable bits
      * to hold the largest element index, i.e. lg2(VLEN) bits.
      */
-    env->vstart = val & ~(~0ULL << ctzl(riscv_cpu_cfg(env)->vlen));
+    env->vstart = val & ~(~0ULL << ctzl(riscv_cpu_cfg(env)->vlenb << 3));
     return RISCV_EXCP_NONE;
 }