net: Allow devices to specify a device specific sysfs group.

This isn't beautifully abstracted, but it is simple,
simplifies uses and so far is only needed for the bonding driver.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 89de182..157645c 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -544,8 +544,11 @@
 	dev_set_name(dev, "%s", net->name);
 
 #ifdef CONFIG_SYSFS
-	*groups++ = &netstat_group;
+	/* Allow for a device specific group */
+	if (*groups)
+		groups++;
 
+	*groups++ = &netstat_group;
 #ifdef CONFIG_WIRELESS_EXT_SYSFS
 	if (net->ieee80211_ptr)
 		*groups++ = &wireless_group;