wifi: mac80211: fix beacon SSID mismatch handling

Return false when memcmp with zero_ssid returns 0 to correctly
handle hidden SSIDs case.

Fixes: 9cc8867 ("wifi: mac80211: check SSID in beacon")
Reviewed-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Signed-off-by: Daniel Gabay <daniel.gabay@intel.com>
Link: https://patch.msgid.link/20240823105546.7ab29ae287a6.I7f98e57e1ab6597614703fdd138cc88ad253d986@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: gabayd

net/mac80211/mlme.c

@@ -6664,7 +6664,7 @@ static bool ieee80211_mgd_ssid_mismatch(struct ieee80211_sub_if_data *sdata,
 		return true;
 
 	/* hidden SSID: zeroed out */
-	if (memcmp(elems->ssid, zero_ssid, elems->ssid_len))
+	if (!memcmp(elems->ssid, zero_ssid, elems->ssid_len))
 		return false;
 
 	return memcmp(elems->ssid, cfg->ssid, cfg->ssid_len);