xen: allocate irq descs on any NUMA node

Allocate irq descs on any NUMA node (we don't care) rather than
specifically node 0, which may not exist.

(At the moment NUMA is meaningless within a domain, so any info
the kernel has is just from an SRAT table we haven't suppressed/disabled.)
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

drivers/xen/events.c

@@ -423,7 +423,7 @@ static int find_unbound_irq(void)
 	if (irq == start)
 		goto no_irqs;
 
-	res = irq_alloc_desc_at(irq, 0);
+	res = irq_alloc_desc_at(irq, -1);
 
 	if (WARN_ON(res != irq))
 		return -1;
@@ -630,7 +630,7 @@ int xen_map_pirq_gsi(unsigned pirq, unsigned gsi, int shareable, char *name)
 	if (identity_mapped_irq(gsi) || (!xen_initial_domain() &&
 				xen_pv_domain())) {
 		irq = gsi;
-		irq_alloc_desc_at(irq, 0);
+		irq_alloc_desc_at(irq, -1);
 	} else
 		irq = find_unbound_irq();