mtd: fix nand kernel-doc warnings

Warning(include/linux/mtd/nand.h:543): No description found for parameter 'badblockbits'
Warning(drivers/mtd/nand/nand_bbt.c:1101): No description found for parameter 'mtd'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc:	David Woodhouse <dwmw2@infradead.org>
Cc:	linux-mtd@lists.infradead.org
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/nand_bbt.c

@@ -1092,7 +1092,8 @@ static void mark_bbt_region(struct mtd_info *mtd, struct nand_bbt_descr *td)
 
 /**
  * verify_bbt_descr - verify the bad block description
- * @bd:			the table to verify
+ * @mtd:	MTD device structure
+ * @bd:		the table to verify
  *
  * This functions performs a few sanity checks on the bad block description
  * table.

include/linux/mtd/nand.h

@@ -448,6 +448,8 @@ struct nand_buffers {
  *			See the defines for further explanation.
  * @badblockpos:	[INTERN] position of the bad block marker in the oob
  *			area.
+ * @badblockbits:	[INTERN] number of bits to left-shift the bad block
+ *			number
  * @cellinfo:		[INTERN] MLC/multichip data from chip ident
  * @numchips:		[INTERN] number of physical chips
  * @chipsize:		[INTERN] the size of one chip for multichip arrays