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/ath/ath9k/init.c

@@ -734,9 +734,11 @@ static const struct ieee80211_iface_limit if_limits[] = {
 				 BIT(NL80211_IFTYPE_P2P_GO) },
 };
 
+#ifdef CONFIG_WIRELESS_WDS
 static const struct ieee80211_iface_limit wds_limits[] = {
 	{ .max = 2048,	.types = BIT(NL80211_IFTYPE_WDS) },
 };
+#endif
 
 #ifdef CONFIG_ATH9K_CHANNEL_CONTEXT
 
@@ -774,6 +776,7 @@ static const struct ieee80211_iface_combination if_comb[] = {
 					BIT(NL80211_CHAN_WIDTH_40),
 #endif
 	},
+#ifdef CONFIG_WIRELESS_WDS
 	{
 		.limits = wds_limits,
 		.n_limits = ARRAY_SIZE(wds_limits),
@@ -781,6 +784,7 @@ static const struct ieee80211_iface_combination if_comb[] = {
 		.num_different_channels = 1,
 		.beacon_int_infra_match = true,
 	},
+#endif
 };
 
 #ifdef CONFIG_ATH9K_CHANNEL_CONTEXT
@@ -851,7 +855,9 @@ static void ath9k_set_hw_capab(struct ath_softc *sc, struct ieee80211_hw *hw)
 			BIT(NL80211_IFTYPE_STATION) |
 			BIT(NL80211_IFTYPE_ADHOC) |
 			BIT(NL80211_IFTYPE_MESH_POINT) |
+#ifdef CONFIG_WIRELESS_WDS
 			BIT(NL80211_IFTYPE_WDS) |
+#endif
 			BIT(NL80211_IFTYPE_OCB);
 
 		if (ath9k_is_chanctx_enabled())