[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/net/irda/irttp.c b/net/irda/irttp.c
index da3f2bc..b55bc8f 100644
--- a/net/irda/irttp.c
+++ b/net/irda/irttp.c
@@ -314,8 +314,8 @@
 		skb_reserve(frag, self->max_header_size);
 
 		/* Copy data from the original skb into this fragment. */
-		memcpy(skb_put(frag, self->max_seg_size), skb->data,
-		       self->max_seg_size);
+		skb_copy_from_linear_data(skb, skb_put(frag, self->max_seg_size),
+			      self->max_seg_size);
 
 		/* Insert TTP header, with the more bit set */
 		frame = skb_push(frag, TTP_HEADER);