net: Allow netdevices to specify needed head/tailroom

This patch adds needed_headroom/needed_tailroom members to struct
net_device and updates many places that allocate sbks to use them. Not
all of them can be converted though, and I'm sure I missed some (I
mostly grepped for LL_RESERVED_SPACE)

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index 89dee43..ed45037 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -710,14 +710,14 @@
 	struct net_device *dev = d->dev;
 	struct sk_buff *skb;
 	struct bootp_pkt *b;
-	int hh_len = LL_RESERVED_SPACE(dev);
 	struct iphdr *h;
 
 	/* Allocate packet */
-	skb = alloc_skb(sizeof(struct bootp_pkt) + hh_len + 15, GFP_KERNEL);
+	skb = alloc_skb(sizeof(struct bootp_pkt) + LL_ALLOCATED_SPACE(dev) + 15,
+			GFP_KERNEL);
 	if (!skb)
 		return;
-	skb_reserve(skb, hh_len);
+	skb_reserve(skb, LL_RESERVED_SPACE(dev));
 	b = (struct bootp_pkt *) skb_put(skb, sizeof(struct bootp_pkt));
 	memset(b, 0, sizeof(struct bootp_pkt));