drm/amdgpu: add initial IP discovery support for vega based parts

Hardcode the IP versions for asics without IP discovery tables
and then enumerate the asics based on the IP versions.

TODO: fix SR-IOV support

v2: Squash in HDP fix for Renoir

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