cfg80211: prohibit zero keepalive interval

It's not useful to specify a 0 keepalive interval, this
would send too much data. Prohibit this to also avoid
device issues.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -7636,7 +7636,8 @@ static int nl80211_parse_wowlan_tcp(struct cfg80211_registered_device *rdev,
 		return -EINVAL;
 
 	if (nla_get_u32(tb[NL80211_WOWLAN_TCP_DATA_INTERVAL]) >
-			rdev->wiphy.wowlan.tcp->data_interval_max)
+			rdev->wiphy.wowlan.tcp->data_interval_max ||
+	    nla_get_u32(tb[NL80211_WOWLAN_TCP_DATA_INTERVAL]) == 0)
 		return -EINVAL;
 
 	wake_size = nla_len(tb[NL80211_WOWLAN_TCP_WAKE_PAYLOAD]);