iris: fix the order of src and dst for fence memcpy

This fixes random failures with "deqp-egl --deqp-case=multithread": iris: Failed to submit batchbuffer: No such file or directory

Fixes: 6b1a56b9 ("iris: Drop stale syncobj references in fence_server_sync") Signed-off-by: Tapani Pälli tapani.palli@intel.com