hw/intc/s390_flic: Fix crash that occurs when saving the machine state

hw/intc/s390_flic: Fix crash that occurs when saving the machine state

adapter_info_so_needed() treats its "opaque" parameter as a S390FLICState,
but the function belongs to a VMStateDescription that is attached to a
TYPE_VIRTIO_CCW_BUS device. This is currently causing a crash when the
user tries to save or migrate the VM state. Fix it by using s390_get_flic()
to get the correct device here instead.

Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Fixes: 9d1b0f5bf5 ("s390_flic: add migration-enabled property")
Message-ID: <20240517061553.564529-1-thuth@redhat.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Tested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>