[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/net/qla3xxx.c b/drivers/net/qla3xxx.c
index 40d2639..7b80fb7 100755
--- a/drivers/net/qla3xxx.c
+++ b/drivers/net/qla3xxx.c
@@ -1927,7 +1927,8 @@
 		 * Copy the ethhdr from first buffer to second. This
 		 * is necessary for 3022 IP completions.
 		 */
-		memcpy(skb_push(skb2, size), skb1->data + VLAN_ID_LEN, size);
+		skb_copy_from_linear_data_offset(skb1, VLAN_ID_LEN,
+						 skb_push(skb2, size), size);
 	} else {
 		u16 checksum = le16_to_cpu(ib_ip_rsp_ptr->checksum);
 		if (checksum &