Use fetchAndStoreOrdered() instead of fetchAndAddOrdered()
Use fetchAndStoreOrdered() instead of fetchAndAddOrdered()

We are only swapping the pointer here, there is no need for a fetch-add
operation. This is motivated by porting ThreadWeaver to CHERI systems
where fetch-add operations on pointers currently require atomic library
functions that are not implemented yet.

KDE/threadweaver,KDE/threadweaver,KDE/threadweaver