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

Now that geometry 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>

test/stream/stream_formats.cpp

@@ -40,10 +40,10 @@ protected:
 			cout << "Failed " << name << endl;
 			cout << "Sizes to test:" << endl;
 			for (Size &size : test)
-				cout << size.toString() << endl;
+				cout << size << endl;
 			cout << "Valid sizes:" << endl;
 			for (Size &size : valid)
-				cout << size.toString() << endl;
+				cout << size << endl;
 
 			return TestFail;
 		}