wireless: deprecate WDS and disable by default

The old WDS 4-addr frame support is very limited, e.g.
 * no encryption is possible on such links
 * it cannot support rate/HT/VHT negotiation
 * management APIs are very restricted

These make the WDS legacy mode useless in practice.

All of these are resolved by the 4-addr AP/client support,
so there's also no reason to improve WDS in the future.

Therefore, add a Kconfig option to disable legacy WDS.
This gives people an "emergency valve" while they migrate
to the better-supported 4-addr AP/client option; we plan
to remove it (and the associated cfg80211/mac80211 code,
which is the ultimate goal) in the future.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/broadcom/b43legacy/main.c

@@ -3838,7 +3838,9 @@ static int b43legacy_wireless_init(struct ssb_device *dev)
 	hw->wiphy->interface_modes =
 		BIT(NL80211_IFTYPE_AP) |
 		BIT(NL80211_IFTYPE_STATION) |
+#ifdef CONFIG_WIRELESS_WDS
 		BIT(NL80211_IFTYPE_WDS) |
+#endif
 		BIT(NL80211_IFTYPE_ADHOC);
 	hw->queues = 1; /* FIXME: hardware has more queues */
 	hw->max_rates = 2;