MIPS: loongson64: set nid for reserved memblock region

Commit 61167ad5("mm: pass nid to reserve_bootmem_region()") reveals
that reserved memblock regions have no valid node id set, just set it
right since loongson64 firmware makes it clear in memory layout info.

This works around booting failure on 3A1000+ since commit 61167ad5


("mm: pass nid to reserve_bootmem_region()") under
CONFIG_DEFERRED_STRUCT_PAGE_INIT.

Signed-off-by: Huang Pei <huangpei@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>