drm/amdgpu: fix signed overrun in amdgpu_ctx_get_fence

Otherwise the first 16 fences of a context will always signal immediately.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>
This commit is contained in:
Christian König 2015-07-18 19:20:05 +02:00 • committed by Alex Deucher
commit cf6f1d3949