nl80211: Make KCK attribute optional in rekey data

New AKM suites like FILS-SHA256 do not use KCK and hence KCK length can
be zero. Add changes to include KCK attribute in rekey data only if the
length is non-zero.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/drivers/driver_nl80211.c

@@ -7755,7 +7755,7 @@ static void nl80211_set_rekey_info(void *priv, const u8 *kek, size_t kek_len,
 	if (!(msg = nl80211_bss_msg(bss, 0, NL80211_CMD_SET_REKEY_OFFLOAD)) ||
 	    !(replay_nested = nla_nest_start(msg, NL80211_ATTR_REKEY_DATA)) ||
 	    nla_put(msg, NL80211_REKEY_DATA_KEK, kek_len, kek) ||
-	    nla_put(msg, NL80211_REKEY_DATA_KCK, kck_len, kck) ||
+	    (kck_len && nla_put(msg, NL80211_REKEY_DATA_KCK, kck_len, kck)) ||
 	    nla_put(msg, NL80211_REKEY_DATA_REPLAY_CTR, NL80211_REPLAY_CTR_LEN,
 		    replay_ctr)) {
 		nl80211_nlmsg_clear(msg);