commit efe2add7 ("spapr/vio: deprecate the "irq" property")
introduced get/set accessors for the "irq" property to warn of its
usage, but the warning in the get pollutes the monitor 'info qtree'.
Signed-off-by: NCédric Le Goater <clg@kaod.org>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>