Fix JFFS2 support for legacy NAND driver.

Some more NAND cleanup and small fixes.
diff --git a/drivers/nand/diskonchip.c b/drivers/nand/diskonchip.c
index afaae83..e17af70 100644
--- a/drivers/nand/diskonchip.c
+++ b/drivers/nand/diskonchip.c
@@ -21,9 +21,7 @@
 
 #include <common.h>
 
-#ifdef CFG_NAND_LEGACY
-#error CFG_NAND_LEGACY defined in a file not using the legacy NAND support!
-#endif
+#if !defined(CFG_NAND_LEGACY)
 
 #include <linux/kernel.h>
 #include <linux/init.h>
@@ -1786,3 +1784,4 @@
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
 MODULE_DESCRIPTION("M-Systems DiskOnChip 2000, Millennium and Millennium Plus device driver\n");
+#endif