drm/amdgpu: mark force completed fences with -ECANCELED

When we force complete fences we should mark them as canceled.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>