drm/amdgpu/vcn: set VCN5 power gating state to GATE on suspend

drm/amdgpu/vcn: set VCN5 power gating state to GATE on suspend

On suspend, we need to set power gating state to GATE when
VCN5 is busy, otherwise we will get following error on resume:

[drm:amdgpu_ring_test_helper [amdgpu]] *ERROR* ring vcn_unified_0 test failed (-110)
[drm:amdgpu_device_ip_resume_phase2 [amdgpu]] *ERROR* resume of IP block <vcn_v5_0_0> failed -110
amdgpu: amdgpu_device_ip_resume failed (-110).
PM: dpm_run_callback(): pci_pm_resume+0x0/0x100 returns -110
PM: failed to resume async: error -110

Signed-off-by: David (Ming Qiang) Wu <David.Wu3@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>