ARM: S3C: NAND: Check the existence of nr_map before copying

Since the structure field nr_map is optional, we need to check whether the
chip number map is provided to avoid unexpected NULL pointer exception.
Signed-off-by: NRamax Lo <ramaxlo@gmail.com>
Signed-off-by: NBen Dooks <ben-linux@fluff.org>

arch/arm/plat-s3c/dev-nand.c

@@ -58,8 +58,8 @@ static int __init s3c_nand_copy_set(struct s3c2410_nand_set *set)
 			return -ENOMEM;
 	}
 	
-	size = sizeof(int) * set->nr_chips;
-	if (size) {
+	if (set->nr_map && set->nr_chips) {
+		size = sizeof(int) * set->nr_chips;
 		ptr = kmemdup(set->nr_map, size, GFP_KERNEL);
 		set->nr_map = ptr;