mtd: nand: Pass mode information to nand_page_io_req

The NAND sub-layers are likely to need the MTD_OPS_XXX mode information
in order to decide if they should enable/disable ECC or how they should
place the OOB bytes in the provided OOB buffer.

Add a field to nand_page_io_req to pass this information.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>