mac80211: Set CAN_REPLACE_PTK0 for SW crypto only drivers

Mac80211 SW crypto handles replacing PTK keys correctly.

Don't trigger needless warnings or workarounds when the driver can only
use the known good SW crypto provided by mac80211.
Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/main.c

@@ -1060,6 +1060,13 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 		wiphy_ext_feature_set(local->hw.wiphy,
 				      NL80211_EXT_FEATURE_EXT_KEY_ID);
 
+	/* Mac80211 and therefore all cards only using SW crypto are able to
+	 * handle PTK rekeys correctly
+	 */
+	if (!local->ops->set_key)
+		wiphy_ext_feature_set(local->hw.wiphy,
+				      NL80211_EXT_FEATURE_CAN_REPLACE_PTK0);
+
 	/*
 	 * Calculate scan IE length -- we need this to alloc
 	 * memory and to subtract from the driver limit. It