iwlwifi: mvm: don't try to offload AES-CMAC in AP/IBSS modes

The firmware/hardware only supports checking AES-CMAC on RX, not
using it on TX. For station mode this is fine, since it's the only
thing it will ever do. For AP mode, it never receives such frames,
but must be able to transmit them. This is currently broken since
we try to enable them for hardware crypto (for RX only) and then
treat them as TX_CMD_SEC_EXT, leading to FIFO underruns during TX
so the frames never go out to the air.

To fix this, simply use software on TX in AP (and IBSS) mode.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c

@@ -2686,8 +2686,12 @@ static int iwl_mvm_mac_set_key(struct ieee80211_hw *hw,
 			 * GTK on AP interface is a TX-only key, return 0;
 			 * on IBSS they're per-station and because we're lazy
 			 * we don't support them for RX, so do the same.
+			 * CMAC in AP/IBSS modes must be done in software.
 			 */
-			ret = 0;
+			if (key->cipher == WLAN_CIPHER_SUITE_AES_CMAC)
+				ret = -EOPNOTSUPP;
+			else
+				ret = 0;
 			key->hw_key_idx = STA_KEY_IDX_INVALID;
 			break;
 		}