<form name="zipcode">
  <div class="form-group">

    <label for="mdphinput" class="control-label">Code de votre département</label>
    
    <input class="form-control" type="text"
           id="mdphinput" name="mdphinput"
           ng-model="mdphinputctrl.zipcode">

    <button class="btn btn-success" type="submit"
            name="submit" alt="Valider"
            ng-if="mdphinputctrl.isOk()"
            ng-click="mdphinputctrl.go()">
      Valider
    </button>
  </div>
</form>

<form name="zipcode">

  <div class="form-inline">
    <label for="mdphinput" class="control-label">Numéro de votre département</label>

    <input class="form-control" type="text"
           id="mdphinput" name="mdphinput"
           ng-model="mdphinputctrl.zipcode">

    <button class="btn btn-success" type="submit"
            name="submit" alt="Valider"
            ng-disabled="!mdphinputctrl.isOk()"
            ng-click="mdphinputctrl.go()">
      Valider
    </button>
  </div>

</form>

Make form inline & disabled button
Make form inline & disabled button
