loongarch: numa: fix compile error

Changelog: 修复编译错误
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>

arch/loongarch/mm/init.c

@@ -72,6 +72,7 @@ void __init paging_init(void)
 	free_area_init(max_zone_pfns);
 }
 
+#ifndef CONFIG_NUMA
 void __init mem_init(void)
 {
 	max_mapnr = max_low_pfn;
@@ -79,6 +80,7 @@ void __init mem_init(void)
 
 	memblock_free_all();
 }
+#endif
 
 void __ref free_initmem(void)
 {