packet_diag: disclose uid value

This value is disclosed via /proc/net/packet but not via netlink messages.
The goal is to have the same level of information.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/packet_diag.h

@@ -32,6 +32,7 @@ enum {
 	PACKET_DIAG_RX_RING,
 	PACKET_DIAG_TX_RING,
 	PACKET_DIAG_FANOUT,
+	PACKET_DIAG_UID,
 
 	__PACKET_DIAG_MAX,
 };