x86: set node_remap_size[0] in fallback path

... otherwise alloc_remap will not get node_mem_map from kva area, and
alloc_node_mem_map has to alloc_bootmem_node to get mem_map.
It will use two low address copies ...
Signed-off-by: NYinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/mm/discontig_32.c

@@ -124,6 +124,7 @@ int __init get_memcfg_numa_flat(void)
 	node_start_pfn[0] = 0;
 	node_end_pfn[0] = max_pfn;
 	memory_present(0, 0, max_pfn);
+	node_remap_size[0] = node_memmap_size_bytes(0, 0, max_pfn);
 
         /* Indicate there is one node available. */
 	nodes_clear(node_online_map);