xen/arm: dom0less: Add #redistributor-regions property to GICv3 node

Dom0less domain using host memory layout may use more than one
re-distributor region (d->arch.vgic.nr_regions > 1). In that case Xen
will add them in a "reg" property of a GICv3 domU node. Guest needs to
know how many regions to search for, and therefore the GICv3 dt binding
[1] specifies that "#redistributor-regions" property is required if more
than one redistributor region is present. However, Xen does not add this
property which makes guest believe, there is just one such region. This
can lead to guest boot failure when doing GIC SMP initialization. Fix it
by adding this property, which matches what we do for hwdom.

[1] Linux: Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml

Fixes: 4809f9ec7d ("xen/arm: if direct-map domain use native addresses for GICv3")
Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>

xen/arch/arm/dom0less-build.c

@@ -176,6 +176,11 @@ static int __init make_gicv3_domU_node(struct kernel_info *kinfo)
     if ( res )
         return res;
 
+    res = fdt_property_cell(fdt, "#redistributor-regions",
+                            d->arch.vgic.nr_regions);
+    if ( res )
+        return res;
+
     /* reg specifies all re-distributors and Distributor. */
     len = (GUEST_ROOT_ADDRESS_CELLS + GUEST_ROOT_SIZE_CELLS) *
           (d->arch.vgic.nr_regions + 1) * sizeof(__be32);