s390x/pci: Send correct event on hotplug

s390x/pci: Send correct event on hotplug

Comit 2c28c490571f ("s390x/pci: let pci devices start in configured mode")
changed the initial state of zPCI devices from ZPCI_FS_STANDBY to
ZPCI_FS_DISABLED (a.k.a. configured). However we still only send a
HP_EVENT_RESERVED_TO_STANDBY event to the guest, indicating a wrong
state.

Let's send a HP_EVENT_TO_CONFIGURED event instead, to match the actual
state the device is in.

This fixes hotplugged devices having to be enabled explicitly in the
guest e.g. via echo 1 > /sys/bus/pci/slots/00000000/power.

On real HW, a PCI device always pops up in the STANDBY state. In QEMU,
we decided to let it show up directly in the configured state (as
configuring it is otherwise just an extra burden for the admin). We can
safely bypass the STANDBY state when hotplugging PCI devices to a guest.

Fixes: 2c28c490571f ("s390x/pci: let pci devices start in configured mode")
Reported-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20190110210358.24035-1-david@redhat.com>
Tested-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Collin Walling <walling@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>