i40e: mark the value passed to csum_replace_by_diff as __wsum

Fix, or rather, avoid a sparse warning caused by the fact that
csum_replace_by_diff expects to receive a __wsum value. Since the
calculation appears to work, simply typecast the passed paylen value to
__wsum to avoid the warning.

This seems pretty fishy since __wsum was obviously annotated as
a separate type on purpose, so this throws the entire calculation into
question. Since it currently appears to behave as expected, the typecast
is probably safe.

Change-ID: I4fdc5cddd589abc16098176e8a61127e761488f4
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -2335,7 +2335,8 @@ static int i40e_tso(struct i40e_tx_buffer *first, u8 *hdr_len,
 
 			/* remove payload length from outer checksum */
 			paylen = skb->len - l4_offset;
-			csum_replace_by_diff(&l4.udp->check, htonl(paylen));
+			csum_replace_by_diff(&l4.udp->check,
+					     (__force __wsum)htonl(paylen));
 		}
 
 		/* reset pointers to inner headers */
@@ -2356,7 +2357,7 @@ static int i40e_tso(struct i40e_tx_buffer *first, u8 *hdr_len,
 
 	/* remove payload length from inner checksum */
 	paylen = skb->len - l4_offset;
-	csum_replace_by_diff(&l4.tcp->check, htonl(paylen));
+	csum_replace_by_diff(&l4.tcp->check, (__force __wsum)htonl(paylen));
 
 	/* compute length of segmentation header */
 	*hdr_len = (l4.tcp->doff * 4) + l4_offset;

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

@@ -1629,7 +1629,8 @@ static int i40e_tso(struct i40e_tx_buffer *first, u8 *hdr_len,
 
 			/* remove payload length from outer checksum */
 			paylen = skb->len - l4_offset;
-			csum_replace_by_diff(&l4.udp->check, htonl(paylen));
+			csum_replace_by_diff(&l4.udp->check,
+					     (__force __wsum)htonl(paylen));
 		}
 
 		/* reset pointers to inner headers */
@@ -1650,7 +1651,7 @@ static int i40e_tso(struct i40e_tx_buffer *first, u8 *hdr_len,
 
 	/* remove payload length from inner checksum */
 	paylen = skb->len - l4_offset;
-	csum_replace_by_diff(&l4.tcp->check, htonl(paylen));
+	csum_replace_by_diff(&l4.tcp->check, (__force __wsum)htonl(paylen));
 
 	/* compute length of segmentation header */
 	*hdr_len = (l4.tcp->doff * 4) + l4_offset;