xen/arm: Fix under-mapping in map_range_to_domain()

If the memory region to be mapped does not start at the page boundary
and its end spans over the page boundary, map_range_to_domain() passes
a number of pages that is short by one to map_regions_p2mt(). Domain's
attempt to access memory within that page will fail. Fix it by calculating
the number of pages to be mapped taking into account the start offset.

Fixes: 88c10b0d6e ("arch/arm: let map_mmio_regions() use start and count")
Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Acked-by: Julien Grall <julien@xen.org>

xen/arch/arm/device.c

@@ -89,7 +89,7 @@ int __overlay_init map_range_to_domain(const struct dt_device_node *dev,
     {
         res = map_regions_p2mt(d,
                                gaddr_to_gfn(addr),
-                               PFN_UP(len),
+                               PFN_UP(addr + len) - PFN_DOWN(addr),
                                maddr_to_mfn(addr),
                                mr_data->p2mt);