net: fix protocol sk_buff field

Commit e992cd9b (kmemcheck: make bitfield annotations truly no-ops
when disabled) allows us to revert a workaround we did in the past to
not add holes in sk_buff structure.

This patch partially reverts commit 14d18a81
(net: fix kmemcheck annotations) so that sparse doesnt complain:

include/linux/skbuff.h:357:41: error: invalid bitfield specifier for
type restricted __be16.
Reported-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -355,8 +355,8 @@ struct sk_buff {
 				ipvs_property:1,
 				peeked:1,
 				nf_trace:1;
-	__be16			protocol:16;
 	kmemcheck_bitfield_end(flags1);
+	__be16			protocol;
 
 	void			(*destructor)(struct sk_buff *skb);
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)