rt2x00: Fix HW crypto key handling

When a crypto key is being removed, rt2x00mac should not
reset the key->hw_key_idx value because that will prevent
the driver from removing the correct key from the hardware.

Furthermore ffz() starts counting at 0 instead of 1, so we don't
need to substract 1 from the resulting value.

Signed-off-by: Stephen Blackheath <[e-mail]>
Signed-off-by: Ivo van Doorn <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

drivers/net/wireless/rt2x00/rt2x00mac.c

···
 	 * provided but key 0 is not, then the key is not found
 	 * by the hardware during RX).
 	 */
-	key->hw_key_idx = 0;
+	if (cmd == SET_KEY)
+		key->hw_key_idx = 0;
 
 	if (key->flags & IEEE80211_KEY_FLAG_PAIRWISE)
 		set_key = rt2x00dev->ops->lib->config_pairwise_key;

drivers/net/wireless/rt2x00/rt61pci.c

···
 		if (reg && reg == mask)
 			return -ENOSPC;
 
-		key->hw_key_idx += reg ? (ffz(reg) - 1) : 0;
+		key->hw_key_idx += reg ? ffz(reg) : 0;
 
 		/*
 		 * Upload key to hardware
···
 				return -ENOSPC;
 		}
 
-		key->hw_key_idx += reg ? (ffz(reg) - 1) : 0;
+		key->hw_key_idx += reg ? ffz(reg) : 0;
 
 		/*
 		 * Upload key to hardware

drivers/net/wireless/rt2x00/rt73usb.c

···
 		if (reg && reg == mask)
 			return -ENOSPC;
 
-		key->hw_key_idx += reg ? (ffz(reg) - 1) : 0;
+		key->hw_key_idx += reg ? ffz(reg) : 0;
 
 		/*
 		 * Upload key to hardware
···
 				return -ENOSPC;
 		}
 
-		key->hw_key_idx += reg ? (ffz(reg) - 1) : 0;
+		key->hw_key_idx += reg ? ffz(reg) : 0;
 
 		/*
 		 * Upload key to hardware