drm/amdgpu/vcn: fix mmsch ctx table size

add jpeg table size to ctx table size rather than override it

Signed-off-by: Jane Jian <Jane.Jian@amd.com>
Reviewed-by: JingWen Chen <JingWen.Chen2@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>