s390x: adapter routes error handling

s390x: adapter routes error handling

If the kernel irqchip has been disabled, we don't want the
{add,release}_adapter_routes routines to call any kvm_irqchip_*
interfaces, as they may rely on an irqchip actually having been
created. Just take a quick exit in that case instead. If you are
trying to use irqfd without a kernel irqchip, we will fail with
an error.

Also initialize routes->gsi[] with -1 in the virtio-ccw handling,
to make sure we don't trip over other errors, either. (Nobody
else uses the gsi array in that structure.)

Fixes: d426d9fba8ea ("s390x/virtio-ccw: wire up irq routing and irqfds")
Reviewed-by: Thomas Huth <thuth@redhat.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20200117111147.5006-1-cohuck@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>