drm/amdgpu: add support for SRIOV in IP discovery path

Handle SRIOV requirements when adding IP blocks.

v2: add comment about UVD/VCE support on vega20 SR-IOV

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>