netfilter: nft_lookup: fix catchall element handling with inverted lookups

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_lookup: fix catchall element handling with inverted lookups nft_lookup_eval() decides whether a lookup matched (`found`) from the direct set lookup and priv->invert before falling back to the catchall element used by interval sets (e.g. nft_set_rbtree) for the open-ended default range. Since `found` is never recomputed after `ext` is replaced by the catchall lookup, inverted lookups (NFT_LOOKUP_F_INV, "!= @set") can wrongly match or wrongly skip the catchall element, producing the wrong verdict. Fold the catchall lookup into `ext` before computing `found`, matching the order already used by nft_objref_map_eval().