rtnl: restore notifications for deleted interfaces

The commit 984ff7a3 is an upstream backport. In fact, it depends on
commit 395eea6ccf2b ("rtnetlink: delay RTM_DELLINK notification until after ndo_uninit()")
which has not been backported in 3.18.y.

Before commit 395eea6ccf2b, 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>