drm/amdgpu: Add instance mask for VCN and JPEG

Keep an instance mask formed by physical instance numbers for VCN and JPEG
IPs. Populate the mask from discovery table information.

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