[SK_BUFF]: Introduce skb_copy_from_linear_data{_offset}

To clearly state the intent of copying from linear sk_buffs, _offset being a
overly long variant but interesting for the sake of saving some bytes.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/drivers/s390/net/qeth_eddp.c b/drivers/s390/net/qeth_eddp.c
index 5890bb5..dd7034f 100644
--- a/drivers/s390/net/qeth_eddp.c
+++ b/drivers/s390/net/qeth_eddp.c
@@ -267,7 +267,8 @@
 
 	QETH_DBF_TEXT(trace, 5, "eddpcdtc");
 	if (skb_shinfo(eddp->skb)->nr_frags == 0) {
-		memcpy(dst, eddp->skb->data + eddp->skb_offset, len);
+		skb_copy_from_linear_data_offset(eddp->skb, eddp->skb_offset,
+						 dst, len);
 		*hcsum = csum_partial(eddp->skb->data + eddp->skb_offset, len,
 				      *hcsum);
 		eddp->skb_offset += len;