numa: handle mmaped memory allocation failure correctly

when memory_region_init_ram_from_file() fails
memory_region_size() will still return size that was
provided at region init time.
Instead use errp to properly detect error condition.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

numa.c

@@ -238,7 +238,7 @@ static void allocate_system_memory_nonnuma(MemoryRegion *mr, Object *owner,
         /* Legacy behavior: if allocation failed, fall back to
          * regular RAM allocation.
          */
-        if (!memory_region_size(mr)) {
+        if (err) {
             qerror_report_err(err);
             error_free(err);
             memory_region_init_ram(mr, owner, name, ram_size);