ath5k: don't change mac in eeprom_read_mac on error

Do not touch mac parameter passed to ath5k_eeprom_read_mac unless
we are sure we have correct address. I.e. when returning error, do
not change it.

While at it, use '= {}' compiler trick for memsetting mac_d.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Nick Kossifidis <mickflemm@gmail.com>
Cc: Luis R. Rodriguez <lrodriguez@atheros.com>
Acked-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath5k/eeprom.c

@@ -1418,14 +1418,11 @@ ath5k_eeprom_init(struct ath5k_hw *ah)
  */
 int ath5k_eeprom_read_mac(struct ath5k_hw *ah, u8 *mac)
 {
-	u8 mac_d[ETH_ALEN];
+	u8 mac_d[ETH_ALEN] = {};
 	u32 total, offset;
 	u16 data;
 	int octet, ret;
 
-	memset(mac, 0, ETH_ALEN);
-	memset(mac_d, 0, ETH_ALEN);
-
 	ret = ath5k_hw_eeprom_read(ah, 0x20, &data);
 	if (ret)
 		return ret;
@@ -1441,11 +1438,11 @@ int ath5k_eeprom_read_mac(struct ath5k_hw *ah, u8 *mac)
 		octet += 2;
 	}
 
-	memcpy(mac, mac_d, ETH_ALEN);
-
 	if (!total || total == 3 * 0xffff)
 		return -EINVAL;
 
+	memcpy(mac, mac_d, ETH_ALEN);
+
 	return 0;
 }