drm/amdgpu/vcn3.0: stall DPG when WPTR/RPTR reset

Port from VCN2.5
Add vcn dpg harware synchronization to fix race condition
issue between vcn driver and hardware.

Signed-off-by: Boyuan Zhang <boyuan.zhang@amd.com>
Reviewed-by: James Zhu <James.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 5.9.x