libcamera: Replace toString with operator<<() for format classes

Now that format classes implement the stream formatting operator<<(),
use it instead of the toString() function.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/pipeline/simple/converter.cpp

@@ -65,8 +65,8 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
 	    format.planes[0].bpl != inputCfg.stride) {
 		LOG(SimplePipeline, Error)
 			<< "Input format not supported (requested "
-			<< inputCfg.size << "-" << videoFormat.toString()
-			<< ", got " << format.toString() << ")";
+			<< inputCfg.size << "-" << videoFormat
+			<< ", got " << format << ")";
 		return -EINVAL;
 	}