linux-phytec-fsl

drm/amdgpu: clear ring pointer in amdgpu_device on teardown

This is in symmetry to setup done in amdgpu_ring_init.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>