anv/image: Do not override lower bits of dword.

anv/image: Do not override lower bits of dword.

The lower bits seem to have extra fields in every platform but gen8
(even though we don't use them in gen9). So just go ahead and avoid
using them for the address.

v4: Use Jason's suggestion for comment explaining the change.
v5: Fix aux_address comment in anv_private.h (Jason)

Signed-off-by: Rafael Antognolli <rafael.antognolli@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>