macvlan: resolve ENOENT errors on creation

After the commit below attempting to create macvlan devices was
resulting in ENOENT errors,

# ip link add link p3p2 type macvlan
RTNETLINK answers: Invalid argument

This happens because netdev_upper_dev_link() is called before
register_netdevice() in the macvlan code. Through a call chain
this results in a call to __netdev_adjacent_dev_insert() and
finally a sysfs_create_link(). This requires the kobject of
the macvlan to be registered which is done in register_netdevice().
If there is no kobject which is the case here the ENOENT error
is seen on the command line.

To resolve this move the netdev_upper_dev_link() call below
the register_netdevice() call. This aligns with vlan driver
flow.

Regression introduced here,

commit 5831d66e
Author: Veaceslav Falico <vfalico@redhat.com>
Date:   Wed Sep 25 09:20:32 2013 +0200

    net: create sysfs symlinks for neighbour devices

CC: Veaceslav Falico <vfalico@redhat.com>
CC: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Veaceslav Falico <vfalico@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>