[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/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
index 3933608..66bef1c 100644
--- a/net/bluetooth/cmtp/core.c
+++ b/net/bluetooth/cmtp/core.c
@@ -124,7 +124,7 @@
 	}
 
 	if (skb && (skb->len > 0))
-		memcpy(skb_put(nskb, skb->len), skb->data, skb->len);
+		skb_copy_from_linear_data(skb, skb_put(nskb, skb->len), skb->len);
 
 	memcpy(skb_put(nskb, count), buf, count);
 
@@ -256,7 +256,7 @@
 			hdr[2] = size >> 8;
 		}
 
-		memcpy(skb_put(nskb, size), skb->data, size);
+		skb_copy_from_linear_data(skb, skb_put(nskb, size), size);
 		skb_pull(skb, size);
 
 		if (skb->len > 0) {