fix comments with new drivers organization

Signed-off-by: Marcel Ziswiler <marcel@ziswiler.com>
diff --git a/common/env_nand.c b/common/env_nand.c
index 38a07f8..ce0a251 100644
--- a/common/env_nand.c
+++ b/common/env_nand.c
@@ -57,7 +57,7 @@
 	    size_t start, size_t len,
 	    size_t * retlen, u_char * buf);
 
-/* info for NAND chips, defined in drivers/nand/nand.c */
+/* info for NAND chips, defined in drivers/mtd/nand/nand.c */
 extern nand_info_t nand_info[];
 
 /* references to names in env_common.c */