Disable A-MSDU support again.

iwm(4) 9k and iwx(4) need more work before AMSDU can be enabled.
These devices decapsulate A-MSDU in hardware and required changes to
make this work with our drivers and stack seem to be non-trivial.

Problems reported by phessler@

ok phessler@

sys/net80211/ieee80211_input.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ieee80211_input.c,v 1.225 2020/12/09 13:24:22 tobhe Exp $	*/
+/*	$OpenBSD: ieee80211_input.c,v 1.226 2020/12/09 15:50:58 stsp Exp $	*/
 
 /*-
  * Copyright (c) 2001 Atsushi Onoe
@@ -2757,7 +2757,10 @@ ieee80211_recv_addba_req(struct ieee80211com *ic, struct mbuf *m,
 	ba->ba_params = (params & IEEE80211_ADDBA_BA_POLICY);
 	ba->ba_params |= ((ba->ba_winsize << IEEE80211_ADDBA_BUFSZ_SHIFT) |
 	    (tid << IEEE80211_ADDBA_TID_SHIFT));
+#if 0
+	/* iwm(4) 9k and iwx(4) need more work before AMSDU can be enabled. */
 	ba->ba_params |= IEEE80211_ADDBA_AMSDU;
+#endif
 	ba->ba_winstart = ssn;
 	ba->ba_winend = (ba->ba_winstart + ba->ba_winsize - 1) & 0xfff;
 	/* allocate and setup our reordering buffer */

sys/net80211/ieee80211_proto.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ieee80211_proto.c,v 1.100 2020/12/08 20:17:32 stsp Exp $	*/
+/*	$OpenBSD: ieee80211_proto.c,v 1.101 2020/12/09 15:50:58 stsp Exp $	*/
 /*	$NetBSD: ieee80211_proto.c,v 1.8 2004/04/30 23:58:20 dyoung Exp $	*/
 
 /*-
@@ -695,7 +695,10 @@ ieee80211_addba_request(struct ieee80211com *ic, struct ieee80211_node *ni,
 	ba->ba_params =
 	    (ba->ba_winsize << IEEE80211_ADDBA_BUFSZ_SHIFT) |
 	    (tid << IEEE80211_ADDBA_TID_SHIFT);
+#if 0
+	/* iwm(4) 9k and iwx(4) need more work before AMSDU can be enabled. */
 	ba->ba_params |= IEEE80211_ADDBA_AMSDU;
+#endif
 	if ((ic->ic_htcaps & IEEE80211_HTCAP_DELAYEDBA) == 0)
 		/* immediate BA */
 		ba->ba_params |= IEEE80211_ADDBA_BA_POLICY;