mtd: nand: bbt: Fix corner case in bad block table handling

In the unlikely event that both blocks 10 and 11 are marked as bad (on a
32 bit machine), then the process of marking block 10 as bad stomps on
cached entry for block 11.  There are (of course) other examples.
Signed-off-by: NPatrick Doyle <pdoyle@irobot.com>
Reviewed-by: NRichard Weinberger <richard@nod.at>
Signed-off-by: NYoshio Furuyama <ytc-mb-yfuruyama7@kioxia.com>
[<miquel.raynal@bootlin.com>: Fixed the title]
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/774a92693f311e7de01e5935e720a179fb1b2468.1616635406.git.ytc-mb-yfuruyama7@kioxia.com

drivers/mtd/nand/bbt.c

@@ -123,7 +123,7 @@ int nanddev_bbt_set_block_status(struct nand_device *nand, unsigned int entry,
 		unsigned int rbits = bits_per_block + offs - BITS_PER_LONG;
 
 		pos[1] &= ~GENMASK(rbits - 1, 0);
-		pos[1] |= val >> rbits;
+		pos[1] |= val >> (bits_per_block - rbits);
 	}
 
 	return 0;