mtd: rawnand: ESMT: Also use the last page for bad block markers

It is known that some ESMT SLC NANDs have been shipped
with the factory bad block markers in the first or last page
of the block, instead of the first or second page. To be on
the safe side, let's check all three locations.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>