mtd: rawnand: arasan: Support the hardware BCH ECC engine

Add support for the hardware ECC BCH engine.

Please mind that this engine has an important limitation:
BCH implementation does not inform the user when an uncorrectable ECC
error occurs. To workaround this, we avoid using the hardware engine
in the read path and do the computation with the software BCH
implementation, which is faster than mixing hardware (for correction)
and software (for verification).

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200519074549.23673-9-miquel.raynal@bootlin.com

drivers/mtd/nand/raw/Kconfig

@@ -456,6 +456,7 @@ config MTD_NAND_CADENCE
 config MTD_NAND_ARASAN
 	tristate "Support for Arasan NAND flash controller"
 	depends on HAS_IOMEM && HAS_DMA
+	select BCH
 	help
 	  Enables the driver for the Arasan NAND flash controller on
 	  Zynq Ultrascale+ MPSoC.