mtd: nand: move NAND_CREATE_EMPTY_BBT flag

The NAND_CREATE_EMPTY_BBT flag was added by commit:
  453281a973c10bce941b240d1c654d536623b16b
  mtd: nand: introduce NAND_CREATE_EMPTY_BBT
This flag is not used within the kernel and not explained well, so I
took the liberty to edit its comments.

Also, this is a BBT-related flag (and closely tied with NAND_BBT_CREATE)
so I'm moving it to bbm.h next to NAND_BBT_CREATE, thus requiring that
we use the flag in nand_chip.bbt_options, *not* in nand_chip.options.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/include/linux/mtd/bbm.h b/include/linux/mtd/bbm.h
index ff18c08..3cf4a8a 100644
--- a/include/linux/mtd/bbm.h
+++ b/include/linux/mtd/bbm.h
@@ -86,6 +86,13 @@
 #define NAND_BBT_VERSION	0x00000100
 /* Create a bbt if none exists */
 #define NAND_BBT_CREATE		0x00000200
+/*
+ * Create an empty BBT with no vendor information. Vendor's information may be
+ * unavailable, for example, if the NAND controller has a different data and OOB
+ * layout or if this information is already purged. Must be used in conjunction
+ * with NAND_BBT_CREATE.
+ */
+#define NAND_CREATE_EMPTY_BBT	0x01000000
 /* Search good / bad pattern through all pages of a block */
 #define NAND_BBT_SCANALLPAGES	0x00000400
 /* Scan block empty during good / bad block scan */