mtd: rawnand: brcmnand: correctly verify erased pages

commit dcb351c0 upstream.

The current code checks that the whole OOB area is erased.
This is a problem when JFFS2 cleanmarkers are added to the OOB, since it will
fail due to the usable OOB bytes not being 0xff.
Correct this by only checking that data and ECC bytes aren't 0xff.

Fixes: 02b88eea ("mtd: brcmnand: Add check for erased page bitflips")
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200512082451.771212-1-noltari@gmail.com


Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>