rt2500usb: write keys to proper registers

Fix rt2500usb hardware encryption broken by commit
96b61bafe22b2f2abcc833d651739edb977f1b1e
"rt2x00: Clean up USB vendor request buffer functions"

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2500usb.c

@@ -376,7 +376,7 @@ static int rt2500usb_config_key(struct rt2x00_dev *rt2x00dev,
 		if (key->hw_key_idx > 0 && crypto->cipher != curr_cipher)
 			return -EOPNOTSUPP;
 
-		rt2500usb_register_multiwrite(rt2x00dev, reg,
+		rt2500usb_register_multiwrite(rt2x00dev, KEY_ENTRY(key->hw_key_idx),
 					      crypto->key, sizeof(crypto->key));
 
 		/*