zink: stop overwriting buffer map pointers for stream uploader
this breaks the driver!
the uploader always maps its own pointer, so modifying that at any point just explodes things later
Fixes: d179c5d2 ("zink: implement threaded context")
this breaks the driver!
the uploader always maps its own pointer, so modifying that at any point just explodes things later
Fixes: d179c5d2 ("zink: implement threaded context")