mac80211: Update to version 5.15-rc6-1

The removed patches were applied upstream.
The Cisco Aironet 802.11b driver was removed from backports, remove
it also from OpenWrt.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

package/kernel/mac80211/patches/subsys/210-ap_scan.patch

@@ -1,6 +1,6 @@
 --- a/net/mac80211/cfg.c
 +++ b/net/mac80211/cfg.c
-@@ -2487,7 +2487,7 @@ static int ieee80211_scan(struct wiphy *
+@@ -2495,7 +2495,7 @@ static int ieee80211_scan(struct wiphy *
  		 * the  frames sent while scanning on other channel will be
  		 * lost)
  		 */