[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/arch/ia64/sn/kernel/xpnet.c b/arch/ia64/sn/kernel/xpnet.c
index 98d7914..9fc0265 100644
--- a/arch/ia64/sn/kernel/xpnet.c
+++ b/arch/ia64/sn/kernel/xpnet.c
@@ -566,7 +566,8 @@
 			msg->version = XPNET_VERSION_EMBED;
 			dev_dbg(xpnet, "calling memcpy(0x%p, 0x%p, 0x%lx)\n",
 				&msg->data, skb->data, (size_t) embedded_bytes);
-			memcpy(&msg->data, skb->data, (size_t) embedded_bytes);
+			skb_copy_from_linear_data(skb, &msg->data,
+						  (size_t)embedded_bytes);
 		} else {
 			msg->version = XPNET_VERSION;
 		}