drm/amdgpu: re-enable retry faults

Now that we have re-reoute faults to the other IH
ring we can enable retries again.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>