anv: fix missing gen12 handling

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 181be14d ("anv: Build for gen12")
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
(cherry picked from commit dcfe1903)