drm/amdgpu: allow secure submission on VCN4 ring

This patch will enable secure decode playback on VCN4_0_2

Signed-off-by: sguttula <Suresh.Guttula@amd.com>
Reviewed-by: Leo Liu <leo.liiu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>