mac80211: remove pointless chanctx NULL check

If chanctx is derived as container_of() from a non-NULL pointer,
it can't ever be NULL. Since we checked conf before, that's true
here, so remove the useless NULL check.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -2961,10 +2961,6 @@ __ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev,
 	}
 
 	chanctx = container_of(conf, struct ieee80211_chanctx, conf);
-	if (!chanctx) {
-		err = -EBUSY;
-		goto out;
-	}
 
 	ch_switch.timestamp = 0;
 	ch_switch.device_timestamp = 0;