libcamera: v4l2_controls: Use the ControlValue class for data storage

Use the ControlValue class to replace the manually crafted data storage
in V4L2Control. This will help sharing code when more data types will be
supported.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/pipeline/uvcvideo.cpp

@@ -252,7 +252,7 @@ int PipelineHandlerUVC::processControls(UVCCameraData *data, Request *request)
 		LOG(UVC, Debug)
 			<< "Setting control 0x"
 			<< std::hex << std::setw(8) << ctrl.id() << std::dec
-			<< " to " << ctrl.value();
+			<< " to " << ctrl.value().toString();
 
 	int ret = data->video_->setControls(&controls);
 	if (ret) {