drm/amdgpu: fix a potential memory leak in amdgpu_device_fini_sw()

amdgpu_fence_driver_sw_fini() should be executed before
amdgpu_device_ip_fini(), otherwise fence driver resource
won't be properly freed as adev->rings have been tore down.

Fixes: 72c8c97b ("drm/amdgpu: Split amdgpu_device_fini into early and late")

Signed-off-by: Lang Yu <lang.yu@amd.com>
Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>