drm/amdgpu: fix shutdown and poweroff process failed with s0ix

In the shutdown and poweroff opt on the s0i3 system we still need
un-gate the gfx clock gating and power gating before destory amdgpu device.

Fixes: 628c36d7 ("drm/amdgpu: update amdgpu device suspend/resume sequence for s0i3 support")
Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1499


Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>