mac80211_hwsim: fix beacon delta calculation

Due to the cast from uint32_t to int64_t, a wrong next beacon timing is
calculated and effectively the beacon timer stops working. This is
especially bad for 802.11s mesh networks, because discovery breaks
without beacons.
Signed-off-by: Benjamin Beichler <benjamin.beichler@uni-rostock.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/mac80211_hwsim.c

@@ -826,7 +826,7 @@ static void mac80211_hwsim_set_tsf(struct ieee80211_hw *hw,
 		data->bcn_delta = do_div(delta, bcn_int);
 	} else {
 		data->tsf_offset -= delta;
-		data->bcn_delta = -do_div(delta, bcn_int);
+		data->bcn_delta = -(s64)do_div(delta, bcn_int);
 	}
 }