mtd: rawnand: fsl_upm: Remove unused mtd var

The mtd var in fun_wait_rnb() is now unused, let's get rid of it and
fix the warning resulting from this unused var.

Fixes: 50a487e7 ("mtd: rawnand: Pass a nand_chip object to chip->dev_ready()")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200603134922.1352340-2-boris.brezillon@collabora.com

drivers/mtd/nand/raw/fsl_upm.c

@@ -62,7 +62,6 @@ static int fun_chip_ready(struct nand_chip *chip)
 static void fun_wait_rnb(struct fsl_upm_nand *fun)
 {
 	if (fun->rnb_gpio[fun->mchip_number] >= 0) {
-		struct mtd_info *mtd = nand_to_mtd(&fun->chip);
 		int cnt = 1000000;
 
 		while (--cnt && !fun_chip_ready(&fun->chip))