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/BMW.h b/include/configs/BMW.h
index bb7856f..11d19c6 100644
--- a/include/configs/BMW.h
+++ b/include/configs/BMW.h
@@ -86,7 +86,7 @@
 
 
 /* CONFIG_CMD_DOC required legacy NAND support */
-#define CFG_NAND_LEGACY
+#define CONFIG_NAND_LEGACY
 
 #if 0
 #define CONFIG_PCI		1