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/GEN860T.h b/include/configs/GEN860T.h
index 037b115..422ed32 100644
--- a/include/configs/GEN860T.h
+++ b/include/configs/GEN860T.h
@@ -280,7 +280,7 @@
 #define CFG_FPGA_PROG_FEEDBACK
 
 
-#define CFG_NAND_LEGACY
+#define CONFIG_NAND_LEGACY
 
 /*
  * Verbose help from command monitor.