net: vlan: avoid leaks on register_vlan_dev() failures

[ Upstream commit 55b7ab11 ]

VLAN checks for NETREG_UNINITIALIZED to distinguish between
registration failure and unregistration in progress.

Since commit cb626bf5 ("net-sysfs: Fix reference count leak")
registration failure may, however, result in NETREG_UNREGISTERED
as well as NETREG_UNINITIALIZED.

This fix is similer to cebb6975 ("rtnetlink: Fix
memory(net_device) leak when ->newlink fails")

Fixes: cb626bf5

 ("net-sysfs: Fix reference count leak")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>