igb: cleanup incorrect comment and set IP Checksum Enable

IP Checksum enable doesn't need packet split in order to function.  It only
requires the use of advanced descriptors which the current igb driver does.
So we can enable it always without any issues.
Signed-off-by: NAlexander Duyck <alexander.h.duyck@intel.com>
Acked-by: NPeter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/igb/igb_main.c

@@ -2059,17 +2059,11 @@ static void igb_configure_rx(struct igb_adapter *adapter)
 	} else {
 		/* Enable Receive Checksum Offload for TCP and UDP */
 		rxcsum = rd32(E1000_RXCSUM);
-		if (adapter->rx_csum) {
-			rxcsum |= E1000_RXCSUM_TUOFL;
+		if (adapter->rx_csum)
+			rxcsum |= E1000_RXCSUM_TUOFL | E1000_RXCSUM_IPPCSE;
+		else
+			rxcsum &= ~(E1000_RXCSUM_TUOFL | E1000_RXCSUM_IPPCSE);
 
-			/* Enable IPv4 payload checksum for UDP fragments
-			 * Must be used in conjunction with packet-split. */
-			if (adapter->rx_ps_hdr_size)
-				rxcsum |= E1000_RXCSUM_IPPCSE;
-		} else {
-			rxcsum &= ~E1000_RXCSUM_TUOFL;
-			/* don't need to clear IPPCSE as it defaults to 0 */
-		}
 		wr32(E1000_RXCSUM, rxcsum);
 	}