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/yuv/post_processor_yuv.cpp

@@ -27,8 +27,8 @@ int PostProcessorYuv::configure(const StreamConfiguration &inCfg,
 {
 	if (inCfg.pixelFormat != outCfg.pixelFormat) {
 		LOG(YUV, Error) << "Pixel format conversion is not supported"
-				<< " (from " << inCfg.pixelFormat.toString()
-				<< " to " << outCfg.pixelFormat.toString() << ")";
+				<< " (from " << inCfg.pixelFormat
+				<< " to " << outCfg.pixelFormat << ")";
 		return -EINVAL;
 	}