drm/amdgpu: Set FRU bus for Aldebaran and Vega 20

The FRU and RAS EEPROMs share the same I2C bus on Aldebaran and Vega 20
ASICs. Set the FRU bus "pointer" to this single bus, as access to the FRU
is sought through that bus "pointer" and not through the RAS bus "pointer".

Cc: Roy Sun <Roy.Sun@amd.com>
Cc: Alex Deucher <Alexander.Deucher@amd.com>
Fixes: 2f60dd50 ("drm/amd: Expose the FRU SMU I2C bus")
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Alex Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>