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/PM826.h b/include/configs/PM826.h
index 36e9aa5..190e2a4 100644
--- a/include/configs/PM826.h
+++ b/include/configs/PM826.h
@@ -180,7 +180,7 @@
 #endif
 
 
-#define CFG_NAND_LEGACY
+#define CONFIG_NAND_LEGACY
 
 /*
  * Disk-On-Chip configuration