netfilter: nft_osf: use enum nft_data_types for nft_validate_register_store

The function nft_validate_register_store requires a struct of type
struct nft_data_types. NFTA_DATA_VALUE is of type enum
nft_verdict_attributes. Pass the correct enum type.

This fixes a warning seen with Clang:
  net/netfilter/nft_osf.c:52:8: warning: implicit conversion from
    enumeration type 'enum nft_data_attributes' to different enumeration
    type 'enum nft_data_types' [-Wenum-conversion]
                                          NFTA_DATA_VALUE, NFT_OSF_MAXGENRELEN);
                                          ^~~~~~~~~~~~~~~

Fixes: b96af92d ("netfilter: nf_tables: implement Passive OS fingerprint module in nft_osf")
Link: https://github.com/ClangBuiltLinux/linux/issues/103


Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>