[ETH]: Combine format_addr() with print_mac().

print_mac() used many most net drivers and format_addr() used by
net-sysfs.c are very similar and they can be intergrated.

format_addr() is also identically redefined in the qla4xxx iscsi
driver.

Export a new function sysfs_format_mac() to be used by net-sysfs,
qla4xxx and others in the future.  Both print_mac() and
sysfs_format_mac() call _format_mac_addr() to do the formatting.

Changed print_mac() to use unsigned char * to be consistent with
net_device struct's dev_addr.  Added buffer length overrun checking
as suggested by Joe Perches.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/if_ether.h b/include/linux/if_ether.h
index cc002cb..7a1e011 100644
--- a/include/linux/if_ether.h
+++ b/include/linux/if_ether.h
@@ -124,12 +124,14 @@
 extern struct ctl_table ether_table[];
 #endif
 
+extern ssize_t sysfs_format_mac(char *buf, const unsigned char *addr, int len);
+
 /*
  *	Display a 6 byte device address (MAC) in a readable format.
  */
-#define MAC_FMT "%02x:%02x:%02x:%02x:%02x:%02x"
-extern char *print_mac(char *buf, const u8 *addr);
-#define DECLARE_MAC_BUF(var) char var[18] __maybe_unused
+extern char *print_mac(char *buf, const unsigned char *addr);
+#define MAC_BUF_SIZE	18
+#define DECLARE_MAC_BUF(var) char var[MAC_BUF_SIZE] __maybe_unused
 
 #endif