mtd: rawnand: Add a NAND_NO_BBM_QUIRK flag

Some controllers with embedded ECC engines override the BBM marker with
data or ECC bytes, thus making bad block detection through bad block
marker impossible. Let's flag those chips so the core knows it shouldn't
check the BBM and consider all blocks good.

This should allow us to get rid of two implementers of the
legacy.block_bad() hook.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200511064917.6255-1-boris.brezillon@collabora.com