rt2x00: clear up IV's on key removal

After looking at code I realized that my previous fix
95844124 ("rt2x00: clear IV's on start to fix AP mode regression")
was incomplete. We can still have wrong IV's after re-keyring.
To fix that, clear up IV's also on key removal.

Fixes: 710e6cc1 ("rt2800: do not nullify initialization vector data")
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
tested-by: Emil Karlson <jekarl@iki.fi>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ralink/rt2x00/rt2800lib.c

@@ -1654,13 +1654,18 @@ static void rt2800_config_wcid_attr_cipher(struct rt2x00_dev *rt2x00dev,
 
 	offset = MAC_IVEIV_ENTRY(key->hw_key_idx);
 
-	rt2800_register_multiread(rt2x00dev, offset,
-				  &iveiv_entry, sizeof(iveiv_entry));
-	if ((crypto->cipher == CIPHER_TKIP) ||
-	    (crypto->cipher == CIPHER_TKIP_NO_MIC) ||
-	    (crypto->cipher == CIPHER_AES))
-		iveiv_entry.iv[3] |= 0x20;
-	iveiv_entry.iv[3] |= key->keyidx << 6;
+	if (crypto->cmd == SET_KEY) {
+		rt2800_register_multiread(rt2x00dev, offset,
+					  &iveiv_entry, sizeof(iveiv_entry));
+		if ((crypto->cipher == CIPHER_TKIP) ||
+		    (crypto->cipher == CIPHER_TKIP_NO_MIC) ||
+		    (crypto->cipher == CIPHER_AES))
+			iveiv_entry.iv[3] |= 0x20;
+		iveiv_entry.iv[3] |= key->keyidx << 6;
+	} else {
+		memset(&iveiv_entry, 0, sizeof(iveiv_entry));
+	}
+
 	rt2800_register_multiwrite(rt2x00dev, offset,
 				   &iveiv_entry, sizeof(iveiv_entry));
 }