drivers/mtd/nand: Move conditional compilation to Makefile

rename CFG_NAND_LEGACY to CONFIG_NAND_LEGACY

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/include/linux/mtd/nand_ids.h b/include/linux/mtd/nand_ids.h
index d9eb911..e7aa26d 100644
--- a/include/linux/mtd/nand_ids.h
+++ b/include/linux/mtd/nand_ids.h
@@ -28,7 +28,7 @@
 #ifndef __LINUX_MTD_NAND_IDS_H
 #define __LINUX_MTD_NAND_IDS_H
 
-#ifndef CFG_NAND_LEGACY
+#ifndef CONFIG_NAND_LEGACY
 #error This module is for the legacy NAND support
 #endif