This routine will be used in the spapr backend. Also introduce a short
xive_alloc_order() helper.
Signed-off-by: NCédric Le Goater <clg@kaod.org>
Reviewed-by: NDavid Gibson <david@gibson.dropbear.id.au>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>