memory hotplug: use macro to switch between section and pfn

Use macro section_nr_to_pfn() to switch between section and pfn, instead
of open-coding it.  No semantic changes.
Signed-off-by: NSheng Yong <shengyong1@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/base/memory.c

@@ -228,7 +228,7 @@ memory_block_action(unsigned long phys_index, unsigned long action, int online_t
 	struct page *first_page;
 	int ret;
 
-	start_pfn = phys_index << PFN_SECTION_SHIFT;
+	start_pfn = section_nr_to_pfn(phys_index);
 	first_page = pfn_to_page(start_pfn);
 
 	switch (action) {

mm/memory_hotplug.c

@@ -502,7 +502,7 @@ int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
 	end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
 
 	for (i = start_sec; i <= end_sec; i++) {
-		err = __add_section(nid, zone, i << PFN_SECTION_SHIFT);
+		err = __add_section(nid, zone, section_nr_to_pfn(i));
 
 		/*
 		 * EEXIST is finally dealt with by ioresource collision