drm/amdgpu/vcn:Scan enc/jpeg fences to init dpg pause new state

Scan enc/jpeg fences to init dpg pause new state in begin use.
It will help set dpg mode to desire state actively.

Signed-off-by: James Zhu <James.Zhu@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>