Until the vfio-ap driver came into live there was a well known
agreement about the way how ap devices are initialized and their
states when the driver's probe function is called.

However, the vfio device driver when receiving an ap queue device does
additional resets thereby removing the registration for interrupts for
the ap device done by the ap bus core code. So when later the vfio
driver releases the device and one of the default zcrypt drivers takes
care of the device the interrupt registration needs to get
renewed. The current code does no renew and result is that requests
send into such a queue will never see a reply processed - the
application hangs.

This patch adds a function which resets the aq queue state machine for
the ap queue device and triggers the walk through the initial states
(which are reset and registration for interrupts). This function is
now called before the driver's probe function is invoked.

When the association between driver and device is released, the
driver's remove function is called. The current implementation calls a
ap queue function ap_queue_remove(). This invokation has been moved to
the ap bus function to make the probe / remove pair for ap bus and
drivers more symmetric.

Fixes: 7e0bdbe5

 ("s390/zcrypt: AP bus support for alternate driver(s)")
Cc: stable@vger.kernel.org # 4.19+
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewd-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewd-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>