[NET]: Restore sanity wrt. print_mac().

MAC_FMT had only one user and we tried to get rid of
that, but this created more problems than it solved.

As a result, this reverts three commits:

235365f3aaaa10b7056293877c0ead50425f25c7 ("net/8021q/vlan_dev.c: Use
print_mac."), fea5fa875eb235dc186b1f5184eb36abc63e26cc ("[NET]: Remove
MAC_FMT"), and 8f789c48448aed74fe1c07af76de8f04adacec7d ("[NET]:
Elminate spurious print_mac() calls.")

Signed-off-by: David S. Miller <[e-mail]>

include/linux/if_ether.h

···
 /*
  *	Display a 6 byte device address (MAC) in a readable format.
  */
-extern __pure char *print_mac(char *buf, const unsigned char *addr);
+extern char *print_mac(char *buf, const unsigned char *addr);
+#define MAC_FMT "%02x:%02x:%02x:%02x:%02x:%02x"
 #define MAC_BUF_SIZE	18
 #define DECLARE_MAC_BUF(var) char var[MAC_BUF_SIZE] __maybe_unused
 

net/8021q/vlan_dev.c

···
 {
 	struct net_device_stats *stats = &dev->stats;
 	struct vlan_ethhdr *veth = (struct vlan_ethhdr *)(skb->data);
-	DECLARE_MAC_BUF(mac);
-	DECLARE_MAC_BUF(mac2);
+
 	/* Handle non-VLAN frames if they are sent to us, for example by DHCP.
 	 *
 	 * NOTE: THIS ASSUMES DIX ETHERNET, SPECIFICALLY NOT SUPPORTING
···
 
 	pr_debug("%s: about to send skb: %p to dev: %s\n",
 		__FUNCTION__, skb, skb->dev->name);
-	pr_debug("  %s %s %4hx %4hx %4hx\n",
-		 print_mac(mac, veth->h_dest), print_mac(mac2, veth->h_source),
+	pr_debug("  " MAC_FMT " " MAC_FMT " %4hx %4hx %4hx\n",
+		 veth->h_dest[0], veth->h_dest[1], veth->h_dest[2],
+		 veth->h_dest[3], veth->h_dest[4], veth->h_dest[5],
+		 veth->h_source[0], veth->h_source[1], veth->h_source[2],
+		 veth->h_source[3], veth->h_source[4], veth->h_source[5],
 		 veth->h_vlan_proto, veth->h_vlan_TCI,
 		 veth->h_vlan_encapsulated_proto);