[riscv-pmp]: PMP_is_locked function has redundant top pmp check

Goal

To remove redundant checks in the function pmp_is_locked

Technical details

https://gitlab.com/qemu-project/qemu/-/blob/master/target/riscv/pmp.c#L45-L58

In the risc-v pmp implementation, the check of top PMP will not change the return value, so consider delete it

static inline int pmp_is_locked(CPURISCVState *env, uint32_t pmp_index)
{

    if (env->pmp_state.pmp[pmp_index].cfg_reg & PMP_LOCK) {
        return 1;
    }
     
    // THIS check is redundant 
    /* Top PMP has no 'next' to check */
    if ((pmp_index + 1u) >= MAX_RISCV_PMPS) {
        return 0;
    }

    return 0;
}

Additional information