r8169: fix the typo in the comment

>From the realtek data sheet, the PID0 should be bit 0.
Signed-off-by: NZhu Yanjun <yanjun.zhu@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169.c

@@ -696,7 +696,7 @@ enum rtl_tx_desc_bit_1 {
 enum rtl_rx_desc_bit {
 	/* Rx private */
 	PID1		= (1 << 18), /* Protocol ID bit 1/2 */
-	PID0		= (1 << 17), /* Protocol ID bit 2/2 */
+	PID0		= (1 << 17), /* Protocol ID bit 0/2 */
 
 #define RxProtoUDP	(PID1)
 #define RxProtoTCP	(PID0)