Merge branch 's390-ism-fixes'

Niklas Schnelle says:

====================
s390/ism: Fixes to client handling

This is v2 of the patch previously titled "s390/ism: Detangle ISM client
IRQ and event forwarding". As suggested by Paolo Abeni I split the patch
up. While doing so I noticed another problem that was fixed by this patch
concerning the way the workqueues access the client structs. This means the
second patch turning the workqueues into simple direct calls also fixes
a problem. Finally I split off a third patch just for fixing
ism_unregister_client()s error path.

The code after these 3 patches is identical to the result of the v1 patch
except that I also turned the dev_err() for still registered DMBs into
a WARN().
====================

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