netfilter: nf_tables: disallow NFTA_SET_ELEM_KEY_END with NFT_SET_ELEM_INTERVAL_END flag

These are mutually exclusive, actually NFTA_SET_ELEM_KEY_END replaces
the flag notation.

Fixes: 7b225d0b5c6d ("netfilter: nf_tables: add NFTA_SET_ELEM_KEY_END attribute")
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/netfilter/nf_tables_api.c

···
 	      nla[NFTA_SET_ELEM_EXPIRATION] ||
 	      nla[NFTA_SET_ELEM_USERDATA] ||
 	      nla[NFTA_SET_ELEM_EXPR] ||
+	      nla[NFTA_SET_ELEM_KEY_END] ||
 	      nla[NFTA_SET_ELEM_EXPRESSIONS]))
 		return -EINVAL;