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/android/mm/generic_camera_buffer.cpp

@@ -66,8 +66,7 @@ CameraBuffer::Private::Private([[maybe_unused]] CameraBuffer *cameraBuffer,
 	const auto &info = PixelFormatInfo::info(pixelFormat);
 	if (!info.isValid()) {
 		error_ = -EINVAL;
-		LOG(HAL, Error) << "Invalid pixel format: "
-				<< pixelFormat.toString();
+		LOG(HAL, Error) << "Invalid pixel format: " << pixelFormat;
 		return;
 	}