CVE-2026-72320: netfilter: nft_lookup: fix catchall element handling with inverted lookups

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nftlookup: fix catchall element handling with inverted lookups

nftlookupeval() 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. nftsetrbtree) for the open-ended default range. Since found is never recomputed after ext is replaced by the catchall lookup, inverted lookups (NFTLOOKUPFINV, "!= @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 nftobjrefmapeval().