mtd: nand: remove unused and buggy get_platform_nandchip() helper function

Nobody uses the get_platform_nandchip() helper function which is supposed
to return a pointer to a platform_nand_chip struct from an mtd_info
pointer.
Moreover, this function is buggy since the introduction of the plat_nand
layer (chip->priv is now storing a pointer to an intermediate
plat_nand_data structure allocated in plat_nand_probe(), and we have no
way to retrieve a pointer to the provided platform_nand_chip struct from
this plat_nand_data pointer).

While we are at it, remove the useless (and buggy, since it's pointing to
something stored on the stack) data->chip.priv assignment.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Fixes: 711fdf627ce1 ("[MTD] [NAND] platform NAND driver: add driver")
Cc: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/plat_nand.c

@@ -56,7 +56,6 @@ static int plat_nand_probe(struct platform_device *pdev)
 	if (IS_ERR(data->io_base))
 		return PTR_ERR(data->io_base);
 
-	data->chip.priv = &data;
 	nand_set_flash_node(&data->chip, pdev->dev.of_node);
 	mtd = nand_to_mtd(&data->chip);
 	mtd->dev.parent = &pdev->dev;

include/linux/mtd/nand.h

@@ -927,15 +927,6 @@ struct platform_nand_data {
 	struct platform_nand_ctrl ctrl;
 };
 
-/* Some helpers to access the data structures */
-static inline
-struct platform_nand_chip *get_platform_nandchip(struct mtd_info *mtd)
-{
-	struct nand_chip *chip = mtd->priv;
-
-	return chip->priv;
-}
-
 /* return the supported features. */
 static inline int onfi_feature(struct nand_chip *chip)
 {