How do I pass a variable through to a custom component without having it evaluated yet?

I have a custom component:

<template>
  <div class="form-group">
    <label for="desc">{{label}}</label>
    <input id="desc" type="text" class="form-control input-sm"
           :name="label"
           :readonly="readonly"
           v-bind:value="value"
           v-on:input="$emit('input', $event.target.value)"
           v-validate="validate"
    />
    <div class="error-feedback">{{ errors.first(label) }}</div>
    {{readonly}}<!-- debugging -->
  </div>
</template>

<script>
export default {
  name: 'FormGroup',
  props: {
    label: String,
    value: String,
    readonly: String,
    validate: String
  },
  data: function() {
    return {
    }
  }
}
</script>

<style scoped>
  .error-feedback {
    color: #cc3333;
  }
</style>

When I call it with:

  <FormGroup label="Channel" readonly="device_config.enabled" validate="required" v-model="device_config.some_setting" />

The custom component receives the 'readonly' property as the literal string "device_config.some_setting" rather than the value contained in device_config.some_setting.

How can I get my custom component to make field readonly dependent on a value in the calling component's model which is passed-in?