dev_set_promiscuity/allmulti might overflow.  Commit: "netdevice: Fix
promiscuity and allmulti overflow" in net-next makes
dev_set_promiscuity/allmulti return error number if overflow happened.

In af_packet, we check all positive increment for promiscuity and
allmulti to get error return.
Signed-off-by: NWang Chen <wangchen@cn.fujitsu.com>
Acked-by: Patrick McHardy <kaber@trash.net> 
Signed-off-by: NDavid S. Miller <davem@davemloft.net>