Assistant: Adding 'qtquickcontrolsstyles' to the list of qch loaded.

Task-number: QTBUG-31692
Change-Id: Ie8e4befc75e0a2df9149c1bf028b88b2572e3148
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Caroline Chao <caroline.chao@digia.com>