netfilter: nf_tables: add NFTA_MASQ_UNSPEC to nft_masq_attributes

To keep this consistent with other nft_*_attributes.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nf_tables.h

@@ -806,6 +806,7 @@ enum nft_nat_attributes {
  * @NFTA_MASQ_FLAGS: NAT flags (see NF_NAT_RANGE_* in linux/netfilter/nf_nat.h) (NLA_U32)
  */
 enum nft_masq_attributes {
+	NFTA_MASQ_UNSPEC,
 	NFTA_MASQ_FLAGS,
 	__NFTA_MASQ_MAX
 };