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/common/cmd_nand.c b/common/cmd_nand.c
index 520c152..fa7a438 100644
--- a/common/cmd_nand.c
+++ b/common/cmd_nand.c
@@ -11,7 +11,7 @@
 #include <common.h>
 
 
-#ifndef CFG_NAND_LEGACY
+#ifndef CONFIG_NAND_LEGACY
 /*
  *
  * New NAND support
@@ -667,7 +667,7 @@
 
 #endif
 
-#else /* CFG_NAND_LEGACY */
+#else /* CONFIG_NAND_LEGACY */
 /*
  *
  * Legacy NAND support - to be phased out
@@ -1077,4 +1077,4 @@
 
 #endif
 
-#endif /* CFG_NAND_LEGACY */
+#endif /* CONFIG_NAND_LEGACY */