[NET]: Make skb->protocol __be16

There are many instances of

	skb->protocol = htons(ETH_P_*);
	skb->protocol = __constant_htons(ETH_P_*);
and
	skb->protocol = *_type_trans(...);

Most of *_type_trans() are already endian-annotated, so, let's shift
attention on other warnings.
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -255,7 +255,7 @@ struct sk_buff {
 				nohdr:1;
 				/* 3 bits spare */
 	__u8			pkt_type;
-	__u16			protocol;
+	__be16			protocol;
 
 	void			(*destructor)(struct sk_buff *skb);
 #ifdef CONFIG_NETFILTER