drm/amdgpu: Fix channel_index table layout for Aldebaran

Fix the channel_index table layout to fetch the correct
channel_index when calculating physical address from
normalized address during page retirement.
Also, fix the number of UMC instances and number of channels
within each UMC instance for Aldebaran.

Signed-off-by: Mukul Joshi <mukul.joshi@amd.com>
Reviewed-By: John Clements <john.clements@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>