[NET]: Wrap netdevice hardware header creation.

Add inline for common usage of hardware header creation, and
fix bug in IPV6 mcast where the assumption about negative return is
an errno. Negative return from hard_header means not enough space
was available,(ie -N bytes).

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 6644e8f..ca8090f 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -434,21 +434,19 @@
 
 	if (build_vlan_header) {
 		/* Now make the underlying real hard header */
-		rc = dev->hard_header(skb, dev, ETH_P_8021Q, daddr, saddr, len + VLAN_HLEN);
-
-		if (rc > 0) {
+		rc = dev_hard_header(skb, dev, ETH_P_8021Q, daddr, saddr,
+				     len + VLAN_HLEN);
+		if (rc > 0)
 			rc += VLAN_HLEN;
-		} else if (rc < 0) {
+		else if (rc < 0)
 			rc -= VLAN_HLEN;
-		}
-	} else {
+	} else
 		/* If here, then we'll just make a normal looking ethernet frame,
 		 * but, the hard_start_xmit method will insert the tag (it has to
 		 * be able to do this for bridged and other skbs that don't come
 		 * down the protocol stack in an orderly manner.
 		 */
-		rc = dev->hard_header(skb, dev, type, daddr, saddr, len);
-	}
+		rc = dev_hard_header(skb, dev, type, daddr, saddr, len);
 
 	return rc;
 }