net: Report dev->promiscuity in netlink reports.

The standard ways of probing a device's promiscuity
(ifi_flags, for instance) does not report the actual
state of the device.  This patch adds dev->promiscuity
to the netlink netdevice report so that users can know
for certain if the device is acting PROMISC or not.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/if_link.h b/include/linux/if_link.h
index 4b24ff4..2f4fa93 100644
--- a/include/linux/if_link.h
+++ b/include/linux/if_link.h
@@ -138,6 +138,8 @@
 	IFLA_GROUP,		/* Group the device belongs to */
 	IFLA_NET_NS_FD,
 	IFLA_EXT_MASK,		/* Extended info mask, VFs, etc */
+	IFLA_PROMISCUITY,	/* Promiscuity count: > 0 means acts PROMISC */
+#define IFLA_PROMISCUITY IFLA_PROMISCUITY
 	__IFLA_MAX
 };