mtd: rawnand: Create a legacy struct and move ->IO_ADDR_{R, W} there

We regularly have new NAND controller drivers that are making use of
fields/hooks that we want to get rid of but can't because of all the
legacy drivers that we might break if we do.

So, instead of removing those fields/hooks, let's move them to a
sub-struct which is clearly documented as deprecated.

We start with the ->IO_ADDR_{R,W] fields.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
diff --git a/drivers/mtd/nand/raw/ndfc.c b/drivers/mtd/nand/raw/ndfc.c
index b96070a..adc4060 100644
--- a/drivers/mtd/nand/raw/ndfc.c
+++ b/drivers/mtd/nand/raw/ndfc.c
@@ -142,8 +142,8 @@
 	struct mtd_info *mtd = nand_to_mtd(chip);
 	int ret;
 
-	chip->IO_ADDR_R = ndfc->ndfcbase + NDFC_DATA;
-	chip->IO_ADDR_W = ndfc->ndfcbase + NDFC_DATA;
+	chip->legacy.IO_ADDR_R = ndfc->ndfcbase + NDFC_DATA;
+	chip->legacy.IO_ADDR_W = ndfc->ndfcbase + NDFC_DATA;
 	chip->cmd_ctrl = ndfc_hwcontrol;
 	chip->dev_ready = ndfc_ready;
 	chip->select_chip = ndfc_select_chip;