drm/amdgpu: fix the hibernation suspend with s0ix

During system hibernation suspend still need un-gate gfx CG/PG firstly to handle HW
status check before HW resource destory.

Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>