drm/amdgpu: avoid over-handle of fence driver fini in s3 test (v2)

In amdgpu_fence_driver_hw_fini, no need to call drm_sched_fini to stop
scheduler in s3 test, otherwise, fence related failure will arrive
after resume. To fix this and for a better clean up, move drm_sched_fini
from fence_hw_fini to fence_sw_fini, as it's part of driver shutdown, and
should never be called in hw_fini.

v2: rename amdgpu_fence_driver_init to amdgpu_fence_driver_sw_init,
to keep sw_init and sw_fini paired.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1668


Fixes: 8d35a259 ("drm/amdgpu: adjust fence driver enable sequence")
Suggested-by: Christian König <christian.koenig@amd.com>
Tested-by: Mike Lothian <mike@fireburn.co.uk>
Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>