You made the same mistake I did 
Just add a comma before "gpu_threads_conf" :
],
"gpu_threads_conf" :
[
Just add a comma before "gpu_threads_conf" :
],
"gpu_threads_conf" :
[
Thanks that solved the syntax issue.
Now it seems to use 2 thread on the AMD and send some compiled code to it but the hash rate seems to stay on 0H/s.