EDIT: It looks like that string works in XMRIG it correctly loaded 2 threads on every card but does not work in xmr-stak-v2.4.3, which opens up a new problem, I can't mine my alt coin with XMRIG because I can't set the algo to stellite/intense or I'm unaware how to.
So I need either a way to run 2 threads in XMR Stak or I need a way to change my algo to stellite or intense (for mining intense coin) in XMRIG.
My fault, xmrig != xmrstak

xmrstak don't have command line options, but you can specify --config /home/miner/config.txt and --amd /home/miner/amd.txt and edit this files after first start miner in autoconf mode.
In amd.txt double all indexes like this:
"gpu_threads_conf" : [
{ "index" : 0, "intensity" : 1152, "worksize" : 8, "affine_to_cpu" : false, "strided_index" : true, "mem_chunk" : 2, "comp_mode" : true },
{ "index" : 0, "intensity" : 1152, "worksize" : 8, "affine_to_cpu" : false, "strided_index" : true, "mem_chunk" : 2, "comp_mode" : true },