libcamera: Use const reference for range loops

Use a const reference in range-based for loops to avoid copies of the
loop elements.

While at it, change looping over controls in
PipelineHandlerUVC::processControls to use structured bindings.

Signed-off-by: Christian Rauch <Rauch.Christian@gmx.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/pipeline_handler.cpp

@@ -616,7 +616,7 @@ void PipelineHandler::disconnect()
 	 */
 	std::vector<std::weak_ptr<Camera>> cameras{ std::move(cameras_) };
 
-	for (std::weak_ptr<Camera> ptr : cameras) {
+	for (const std::weak_ptr<Camera> &ptr : cameras) {
 		std::shared_ptr<Camera> camera = ptr.lock();
 		if (!camera)
 			continue;