intel: devinfo: silence coverity warning

It's just not possible to have a device with no subslices.

CID: 1433511
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>

src/intel/dev/gen_device_info.c

@@ -1034,6 +1034,7 @@ gen_device_info_update_from_topology(struct gen_device_info *devinfo,
       }
       n_subslices += devinfo->num_subslices[s];
    }
+   assert(n_subslices > 0);
 
    uint32_t eu_mask_len =
       topology->eu_stride * topology->max_subslices * topology->max_slices;