ath11k: clear the keys properly via DISABLE_KEY

DISABLE_KEY sets the key_len to 0, firmware will not delete the keys if
key_len is 0. Changing from security mode to open mode will cause mcast
to be still encrypted without vdev restart.

Set the proper key_len for DISABLE_KEY cmd to clear the keys in
firmware.

Tested-on: IPQ6018 hw1.0 AHB WLAN.HK.2.5.0.1-01100-QCAHKSWPL_SILICONZ-1

Fixes: d5c65159 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Reported-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Karthikeyan Kathirvel <kathirve@codeaurora.org>
[sven@narfation.org: split into separate patches, clean up commit message]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211115100441.33771-1-sven@narfation.org

drivers/net/wireless/ath/ath11k/mac.c

@@ -3461,9 +3461,7 @@ static int ath11k_install_key(struct ath11k_vif *arvif,
 		return 0;
 
 	if (cmd == DISABLE_KEY) {
-		/* TODO: Check if FW expects  value other than NONE for del */
-		/* arg.key_cipher = WMI_CIPHER_NONE; */
-		arg.key_len = 0;
+		arg.key_cipher = WMI_CIPHER_NONE;
 		arg.key_data = NULL;
 		goto install;
 	}

drivers/net/wireless/ath/ath11k/wmi.c

@@ -1725,6 +1725,7 @@ int ath11k_wmi_vdev_install_key(struct ath11k *ar,
 	tlv = (struct wmi_tlv *)(skb->data + sizeof(*cmd));
 	tlv->header = FIELD_PREP(WMI_TLV_TAG, WMI_TAG_ARRAY_BYTE) |
 		      FIELD_PREP(WMI_TLV_LEN, key_len_aligned);
+	if (arg->key_data)
 		memcpy(tlv->value, (u8 *)arg->key_data, key_len_aligned);
 
 	ret = ath11k_wmi_cmd_send(wmi, skb, WMI_VDEV_INSTALL_KEY_CMDID);