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/configs/NETVIA.h b/include/configs/NETVIA.h
index 1293fb0..c029594 100644
--- a/include/configs/NETVIA.h
+++ b/include/configs/NETVIA.h
@@ -397,7 +397,7 @@
 
 /*****************************************************************************/
 
-#define CFG_NAND_LEGACY
+#define CONFIG_NAND_LEGACY
 
 #if defined(CONFIG_NETVIA_VERSION) && CONFIG_NETVIA_VERSION >= 2