mtd: nand: hide in-memory BBT implementation details

nand_base.c shouldn't have to know the implementation details of
nand_bbt's in-memory BBT. Specifically, nand_base shouldn't perform the
bit masking and shifting to isolate a BBT entry.

Instead, just move some of the BBT code into a new nand_markbad_bbt()
interface. This interface allows external users (i.e., nand_base) to
mark a single block as bad in the BBT. Then nand_bbt will take care of
modifying the in-memory BBT and updating the flash-based BBT (if
applicable).

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 0745a42..9f7b248 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -628,8 +628,8 @@
 extern struct nand_manufacturers nand_manuf_ids[];
 
 extern int nand_scan_bbt(struct mtd_info *mtd, struct nand_bbt_descr *bd);
-extern int nand_update_bbt(struct mtd_info *mtd, loff_t offs);
 extern int nand_default_bbt(struct mtd_info *mtd);
+extern int nand_markbad_bbt(struct mtd_info *mtd, loff_t offs);
 extern int nand_isbad_bbt(struct mtd_info *mtd, loff_t offs, int allowbbt);
 extern int nand_erase_nand(struct mtd_info *mtd, struct erase_info *instr,
 			   int allowbbt);