drm/amdgpu: fix timeout calculation

Signed-off-by: Christian König <[e-mail]>
Reviewed-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c

···
 	if (((int64_t)timeout_ns) < 0)
 		return MAX_SCHEDULE_TIMEOUT;
 
-	timeout = ktime_sub_ns(ktime_get(), timeout_ns);
+	timeout = ktime_sub(ns_to_ktime(timeout_ns), ktime_get());
 	if (ktime_to_ns(timeout) < 0)
 		return 0;