IB/core: Fix oops in netdev_next_upper_dev_rcu()

When support for bonding of RoCE devices was added, there was
necessarily a link between the RoCE device and the paired netdevice that
was part of the bond.  If you remove the mlx4_en module, that paired
association is broken (the RoCE device is still present but the paired
netdevice has been released).  We need to account for this in
is_upper_ndev_bond_master_filter() and filter out those links with a
broken pairing or else we later oops in netdev_next_upper_dev_rcu().

Fixes: 408f1242 ("IB/core: Delete lower netdevice default GID entries in bonding scenario")
Signed-off-by: Mark Zhang <markz@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>