drm/amd/amdgpu: add instance_number check in amdgpu_discovery_get_ip_version

The original code returns IP version of instantce_0 for every IP. This implementation may be correct for most of IPs.

However, for certain IP block (VCN for example), it may have 2 instances and
both of them have the same hw_id, BUT they have different revision number (0 and 1).

In this case, the original amdgpu_discovery_get_ip_version cannot correct reflects
the result and returns false information

Signed-off-by: Bokun Zhang <Bokun.Zhang@amd.com>
Signed-off-by: Peng Ju Zhou <PengJu.Zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>