<?php
function google_map_autofill_form_alter(&$form, &$form_state, $form_id) {
  if(in_array($form_id,['user_form','user_edit_form'])) {
    $form['field_google_map']['#disabled'] = 'disabled';
  }
  if(in_array($form_id,['user-register-form','user_register_form'])) {
    $form['field_google_map']['#disabled'] = 'disabled';
  }
}

function google_map_autofill_entity_presave(Drupal\Core\Entity\EntityInterface $entity) {
  if($entity->bundle() == "user"){
    //get content from field_address and check it for linebreaks; if linebreaks exist replace them with single space
    $address = trim(preg_replace('/\s+/', ' ', $entity->field_address->value));
    //set field_google_map value to equal field_address
    $entity->field_google_map->value = $address;
    //save is done automatically
  }
}