mm/page_alloc.c: remove unused struct zone *z variable

Remove unused struct zone *z variable which appeared in 86051ca5eaf5
("mm: fix usemap initialization").

Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -4490,7 +4490,6 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 	unsigned long end_pfn = start_pfn + size;
 	pg_data_t *pgdat = NODE_DATA(nid);
 	unsigned long pfn;
-	struct zone *z;
 	unsigned long nr_initialised = 0;
 
 	if (highest_memmap_pfn < end_pfn - 1)
@@ -4503,7 +4502,6 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 	if (altmap && start_pfn == altmap->base_pfn)
 		start_pfn += altmap->reserve;
 
-	z = &pgdat->node_zones[zone];
 	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
 		/*
 		 * There can be holes in boot-time mem_map[]s