libcamera: Remove buffer index from logging

The buffer index is a V4L2 concept that will be hidden from users with
the introduction of a new FrameBuffer class. In preparation for this,
remove the index from log messages.

Keep and move one debug log message where the index is available as the
V4L2 buffer is being dequeued for the video device and it's useful when
debugging.

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

test/v4l2_videodevice/capture_async.cpp

@@ -22,7 +22,7 @@ public:
 
 	void receiveBuffer(Buffer *buffer)
 	{
-		std::cout << "Received buffer " << buffer->index() << std::endl;
+		std::cout << "Buffer received" << std::endl;
 		frames++;
 
 		/* Requeue the buffer for further use. */