Re-factoring the legacy NAND code (legacy NAND now only in board-specific

code and in SoC code). Boards using the old way have CFG_NAND_LEGACY and
BOARDLIBS = drivers/nand_legacy/libnand_legacy.a added. Build breakage for
NETTA.ERR and NETTA_ISDN - will go away when the new NAND support is
implemented for these boards.

drivers/nand/nand.c

@@ -23,7 +23,10 @@
 
 #include <common.h>
 
-#ifdef CONFIG_NEW_NAND_CODE
+#ifdef CFG_NAND_LEGACY
+#error CFG_NAND_LEGACY defined in a file not using the legacy NAND support!
+#endif
+
 #if (CONFIG_COMMANDS & CFG_CMD_NAND)
 
 #include <nand.h>
@@ -72,5 +75,3 @@ void nand_init(void)
 }
 
 #endif
-#endif /* CONFIG_NEW_NAND_CODE */
-