On Arcturus, data fabric hashing is set by the VBIOS, and
affects which addresses map to which memory channels. The
gfx core's caches also need to know this mapping, but the
hash settings for these these caches is set by the driver.

This change queries the DF to understand how the VBIOS
configured DF, then matches the TC hash configuration bits
to do the same thing.

v2: squash in warning fix
Signed-off-by: Joseph Greathouse <Joseph.Greathouse@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>