The available Qt5 modules as of Qt 5.7 in morty OpenEmbedded can be seen here. Are you referring to the QtWebEngine? The qt5 toolchain packagegroup does not seem to include webengine. May be adding it and rebuilding the SDK might work. I once had to do the same for a project relying on Qt charts module since it does not get included in the SDK by default.
If webview module is different, then it seems the meta-qt5 layer does not have a recipe for it yet. You probably have to create a new recipe to let OpenEmbedded compile this component.