mtd: nand: Create a helper to extract the ECC configuration

Despite its current name, the eccreq field actually encodes both the
NAND requirements and the final ECC configuration. That works fine when
using on-die ECC since those 2 concepts match perfectly, but it starts
being a problem as soon as we use on-host ECC engines, where we're not
guaranteed to have a perfect match.

Let's hide the ECC configuration access behind a helper so we can later
split those 2 concepts.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200827085208.16276-12-miquel.raynal@bootlin.com

include/linux/mtd/nand.h

@@ -523,6 +523,16 @@ nanddev_get_memorg(struct nand_device *nand)
 	return &nand->memorg;
 }
 
+/**
+ * nanddev_get_ecc_conf() - Extract the ECC configuration from a NAND device
+ * @nand: NAND device
+ */
+static inline const struct nand_ecc_props *
+nanddev_get_ecc_conf(struct nand_device *nand)
+{
+	return &nand->eccreq;
+}
+
 int nanddev_init(struct nand_device *nand, const struct nand_ops *ops,
 		 struct module *owner);
 void nanddev_cleanup(struct nand_device *nand);