arm64: mm: simplify memblock numa node extraction

We currently open-code extracting the NUMA node of a memblock region,
which requires an ifdef to cater for !CONFIG_NUMA builds where the
memblock_region::nid field does not exist.

The generic memblock_get_region_node helper is intended to cater for
this. For CONFIG_HAVE_MEMBLOCK_NODE_MAP, builds this returns reg->nid,
and for for !CONFIG_HAVE_MEMBLOCK_NODE_MAP builds this is a static
inline that returns 0. Note that for arm64,
CONFIG_HAVE_MEMBLOCK_NODE_MAP is selected iff CONFIG_NUMA is.

This patch makes use of memblock_get_region_node to simplify the arm64
code. At the same time, we can move the nid variable definition into the
loop, as this is the only place it is used.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/init.c

@@ -160,12 +160,10 @@ static void __init arm64_memory_present(void)
 static void __init arm64_memory_present(void)
 {
 	struct memblock_region *reg;
-	int nid = 0;
 
 	for_each_memblock(memory, reg) {
-#ifdef CONFIG_NUMA
-		nid = reg->nid;
-#endif
+		int nid = memblock_get_region_node(reg);
+
 		memory_present(nid, memblock_region_memory_base_pfn(reg),
 				memblock_region_memory_end_pfn(reg));
 	}