rtnl: restore notifications for deleted interfaces

The commit 984ff7a3 is an upstream backport. In fact, it depends on
commit 395eea6c ("rtnetlink: delay RTM_DELLINK notification until after ndo_uninit()")
which has not been backported in 3.18.y.

Before commit 395eea6c, rollback_registered_many() uses rtmsg_ifinfo().
The call to this function is done with dev->reg_state set to
NETREG_UNREGISTERING, thus testing this reg_state in rtmsg_ifinfo() is
wrong.

This patch partially reverts commit 984ff7a3.

Fixes: 984ff7a3 ("rtnl/bond: don't send rtnl msg for unregistered iface")
Reported-by: Kristian Evensen <kristian.evensen@gmail.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

net/core/rtnetlink.c

@@ -2229,9 +2229,6 @@ void rtmsg_ifinfo(int type, struct net_device *dev, unsigned int change,
 	int err = -ENOBUFS;
 	size_t if_info_size;
 
-	if (dev->reg_state != NETREG_REGISTERED)
-		return;
-
 	skb = nlmsg_new((if_info_size = if_nlmsg_size(dev, 0)), flags);
 	if (skb == NULL)
 		goto errout;