mm/mem-hotplug: replace simple_strtoull() with kstrtoull()

Use the newer and more pleasant kstrtoull() to replace
simple_strtoull(), because simple_strtoull() is marked for obsoletion.

Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 7c60ed2..a2e13e2 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -406,7 +406,9 @@
 	int i, ret;
 	unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;
 
-	phys_addr = simple_strtoull(buf, NULL, 0);
+	ret = kstrtoull(buf, 0, &phys_addr);
+	if (ret)
+		return ret;
 
 	if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
 		return -EINVAL;