xen/arm: fix math in add_hwdom_free_regions

Erroneous logic was duplicated from add_ext_regions() into
add_hwdom_free_regions(). Frame numbers are converted to addresses, but
the end address (e) is rounded down to page size alignment. The logic to
calculate the size assumes e points to the last address, not page,
effectively leading to the region size being erroneously calculated to
be 2M smaller than the actual size of the region.

Fix by adding 1 to the frame number before converting back to address.

Fixes: 02975cc383 ("xen/arm: permit non direct-mapped Dom0 construction")
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
Acked-by: Michal Orzel <michal.orzel@amd.com>

xen/common/device-tree/domain-build.c

@@ -109,7 +109,7 @@ static int __init add_hwdom_free_regions(unsigned long s_gfn,
     struct membanks *free_regions = data;
     paddr_t start, size;
     paddr_t s = pfn_to_paddr(s_gfn);
-    paddr_t e = pfn_to_paddr(e_gfn);
+    paddr_t e = pfn_to_paddr(e_gfn + 1) - 1;
     unsigned int i, j;
 
     if ( free_regions->nr_banks >= free_regions->max_banks )