drm/amdgpu/vg20:Add IH client ID for the 2nd UVD

For Vega20, there are two UVD hardware. Need add
the 2nd IH client ID for the 2nd UVD Hardware.

Signed-off-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>