mtd: rawnand: tegra: check bounds of die_nr properly

The Tegra driver currently only support a single chip select, hence
check boundaries accordingly. This fixes a off by one issue catched
with Smatch:
    drivers/mtd/nand/raw/tegra_nand.c:476 tegra_nand_select_chip()
    warn: array off by one? 'nand->cs[die_nr]'

Also warn in case the stack asks for a chip select we currently do
not support.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/nand/raw/tegra_nand.c

@@ -468,7 +468,9 @@ static void tegra_nand_select_chip(struct mtd_info *mtd, int die_nr)
 	struct tegra_nand_chip *nand = to_tegra_chip(chip);
 	struct tegra_nand_controller *ctrl = to_tegra_ctrl(chip->controller);
 
-	if (die_nr < 0 || die_nr > 1) {
+	WARN_ON(die_nr >= (int)ARRAY_SIZE(nand->cs));
+
+	if (die_nr < 0 || die_nr > 0) {
 		ctrl->cur_cs = -1;
 		return;
 	}