[NET]: Wrap hard_header_parse

Wrap the hard_header_parse function to simplify next step of
header_ops conversion.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 2aaf6fa..bdeb2f0 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -207,9 +207,9 @@
  * @skb: packet to extract header from
  * @haddr: destination buffer
  */
-static int eth_header_parse(struct sk_buff *skb, unsigned char *haddr)
+static int eth_header_parse(const struct sk_buff *skb, unsigned char *haddr)
 {
-	struct ethhdr *eth = eth_hdr(skb);
+	const struct ethhdr *eth = eth_hdr(skb);
 	memcpy(haddr, eth->h_source, ETH_ALEN);
 	return ETH_ALEN;
 }