Allow us to query instances versions more cleanly.

Instancing support is not consistent unfortunately. SDMA is a
good example.  Sienna cichlid has 4 total SDMA instances, each
enumerated separately (HWIDs 42, 43, 68, 69).  Arcturus has 8
total SDMA instances, but they are enumerated as multiple
instances of the same HWIDs (4x HWID 42, 4x HWID 43).  UMC
is another example.  On most chips there are multiple
instances with the same HWID.  This allows us to support both
forms.

v2: rebase
v3: clarify instancing support
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>