nl80211: clarify code in nl80211_del_station()

The long if chain of interface types is hard to read,
especially now with the additional condition after it.
Use a switch statement to clarify this code.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20200320113834.2c51b9e8e341.I3fa5dc3f7d3cb1dbbd77191d764586f7da993f3f@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -6285,16 +6285,22 @@ static int nl80211_del_station(struct sk_buff *skb, struct genl_info *info)
 	if (info->attrs[NL80211_ATTR_MAC])
 		params.mac = nla_data(info->attrs[NL80211_ATTR_MAC]);
 
-	if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_AP &&
-	    dev->ieee80211_ptr->iftype != NL80211_IFTYPE_AP_VLAN &&
-	    dev->ieee80211_ptr->iftype != NL80211_IFTYPE_MESH_POINT &&
-	    dev->ieee80211_ptr->iftype != NL80211_IFTYPE_P2P_GO &&
-	    dev->ieee80211_ptr->iftype != NL80211_IFTYPE_ADHOC)
+	switch (dev->ieee80211_ptr->iftype) {
+	case NL80211_IFTYPE_AP:
+	case NL80211_IFTYPE_AP_VLAN:
+	case NL80211_IFTYPE_MESH_POINT:
+	case NL80211_IFTYPE_P2P_GO:
+		/* always accept these */
+		break;
+	case NL80211_IFTYPE_ADHOC:
+		/* conditionally accept */
+		if (wiphy_ext_feature_isset(&rdev->wiphy,
+					    NL80211_EXT_FEATURE_DEL_IBSS_STA))
+			break;
 		return -EINVAL;
-	if (dev->ieee80211_ptr->iftype == NL80211_IFTYPE_ADHOC &&
-	    !wiphy_ext_feature_isset(&rdev->wiphy,
-				     NL80211_EXT_FEATURE_DEL_IBSS_STA))
+	default:
 		return -EINVAL;
+	}
 
 	if (!rdev->ops->del_station)
 		return -EOPNOTSUPP;