nand: reinstate lazy bad block scanning

commit 2a8e0fc8b3dc31a3c571e439fbf04b882c8986be ("nand: Merge changes
from Linux nand driver") accidentally reverted commit
13f0fd94e3cae6f8a0d9fba5d367e311edc8ebde ("NAND: Scan bad blocks
lazily.").

Reinstate the change, as amended by commit
ff49ea8977b56916edd5b1766d9939010e30b181 ("NAND: Mark the BBT as scanned
prior to calling scan_bbt.").

Signed-off-by: Scott Wood <scottwood@freescale.com>
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 99668d5..da6fa18 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -232,6 +232,8 @@
 #define NAND_CREATE_EMPTY_BBT		0x01000000
 
 /* Options set by nand scan */
+/* bbt has already been read */
+#define NAND_BBT_SCANNED	0x40000000
 /* Nand scan has allocated controller struct */
 #define NAND_CONTROLLER_ALLOC	0x80000000