memblock: fix crash when reserved memory is not added to memory

After commit 61167ad ("mm: pass nid to reserve_bootmem_region()")
nid of a reserved region is used by init_reserved_page() (with
CONFIG_DEFERRED_STRUCT_PAGE_INIT=y) to access node strucure.
In many cases the nid of the reserved memory is not set and this causes
a crash.

When the nid of a reserved region is not set, fall back to
early_pfn_to_nid(), so that nid of the first_online_node will be passed
to init_reserved_page().

Fixes: 61167ad ("mm: pass nid to reserve_bootmem_region()")
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Link: https://lore.kernel.org/r/20240118061853.2652295-1-yajun.deng@linux.dev
[rppt: massaged the commit message]
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>

Author: Yajun Deng

mm/memblock.c

@@ -2141,6 +2141,9 @@ static void __init memmap_init_reserved_pages(void)
 			start = region->base;
 			end = start + region->size;
 
+			if (nid == NUMA_NO_NODE || nid >= MAX_NUMNODES)
+				nid = early_pfn_to_nid(PFN_DOWN(start));
+
 			reserve_bootmem_region(start, end, nid);
 		}
 	}