Merge branch 's390-qeth-next'

Julian Wiedmann says:

====================
s390/qeth: updates 2019-01-25

please apply a first batch of qeth patches for net-next, primarily touching the
net_device parts of the driver.
In addition to the usual refactoring & code consolidation, patch 7 makes use of
netif_device_detach() to let the stack know when our control plane is down. This
helps quite a bit wrt to overall locking and proper init/shutdown sequencing.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>