net: ethernet: Use swap() instead of open coding it

Clean the following coccicheck warning:

./drivers/net/ethernet/sunplus/spl2sw_driver.c:217:27-28: WARNING
opportunity for swap().

./drivers/net/ethernet/sunplus/spl2sw_driver.c:222:27-28: WARNING
opportunity for swap().
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sunplus/spl2sw_driver.c

@@ -204,28 +204,16 @@ static const struct net_device_ops netdev_ops = {
 
 static void spl2sw_check_mac_vendor_id_and_convert(u8 *mac_addr)
 {
-	u8 tmp;
-
 	/* Byte order of MAC address of some samples are reversed.
 	 * Check vendor id and convert byte order if it is wrong.
 	 * OUI of Sunplus: fc:4b:bc
 	 */
 	if (mac_addr[5] == 0xfc && mac_addr[4] == 0x4b && mac_addr[3] == 0xbc &&
 	    (mac_addr[0] != 0xfc || mac_addr[1] != 0x4b || mac_addr[2] != 0xbc)) {
-		/* Swap mac_addr[0] and mac_addr[5] */
-		tmp = mac_addr[0];
-		mac_addr[0] = mac_addr[5];
-		mac_addr[5] = tmp;
-
-		/* Swap mac_addr[1] and mac_addr[4] */
-		tmp = mac_addr[1];
-		mac_addr[1] = mac_addr[4];
-		mac_addr[4] = tmp;
-
-		/* Swap mac_addr[2] and mac_addr[3] */
-		tmp = mac_addr[2];
-		mac_addr[2] = mac_addr[3];
-		mac_addr[3] = tmp;
+
+		swap(mac_addr[0], mac_addr[5]);
+		swap(mac_addr[1], mac_addr[4]);
+		swap(mac_addr[2], mac_addr[3]);
 	}
 }