[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/7990.c b/drivers/net/7990.c
index c50264a..d396f99 100644
--- a/drivers/net/7990.c
+++ b/drivers/net/7990.c
@@ -567,7 +567,7 @@
 
     	if (skb->len < ETH_ZLEN)
     		memset((char *)&ib->tx_buf[entry][0], 0, ETH_ZLEN);
-        memcpy ((char *)&ib->tx_buf [entry][0], skb->data, skblen);
+        skb_copy_from_linear_data(skb, &ib->tx_buf[entry][0], skblen);
 
         /* Now, give the packet to the lance */
         ib->btx_ring [entry].tmd1_bits = (LE_T1_POK|LE_T1_OWN);