Recently we added code to properly clean away VIO CRQs on reset  However,
this directly uses qemu_register, rather than the existing device model
reset callbacks.  This patch cleans this up by adding proper use of the
reset hook to the VIO bus model.  The existing CRQ reset code is converted
to the new method.
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NAndreas Färber <afaerber@suse.de>