libcamera: PixelFormat: Turn into a class

Create a class to represent a pixel format. This is done to add support
for modifiers for the formats. So far no modifiers are added by any
pipeline handler, all plumbing to deal with them is however in place.

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

src/libcamera/stream.cpp

@@ -347,9 +347,7 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
  */
 std::string StreamConfiguration::toString() const
 {
-	std::stringstream ss;
-	ss << size.toString() << "-" << utils::hex(pixelFormat);
-	return ss.str();
+	return size.toString() + "-" + pixelFormat.toString();
 }
 
 /**