pinctrl: at91: Fix possible out-of-boundary access

at91_gpio_probe() doesn't check that given OF alias is not available or
something went wrong when trying to get it. This might have consequences
when accessing gpio_chips array with that value as an index. Note, that
BUG() can be compiled out and hence won't actually perform the required
checks.

Fixes: 6732ae5 ("ARM: at91: add pinctrl support")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Closes: https://lore.kernel.org/r/202505052343.UHF1Zo93-lkp@intel.com/
Link: https://lore.kernel.org/20250508200807.1384558-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: andy-shev

drivers/pinctrl/pinctrl-at91.c

@@ -1822,12 +1822,16 @@ static int at91_gpio_probe(struct platform_device *pdev)
 	struct at91_gpio_chip *at91_chip = NULL;
 	struct gpio_chip *chip;
 	struct pinctrl_gpio_range *range;
+	int alias_idx;
 	int ret = 0;
 	int irq, i;
-	int alias_idx = of_alias_get_id(np, "gpio");
 	uint32_t ngpio;
 	char **names;
 
+	alias_idx = of_alias_get_id(np, "gpio");
+	if (alias_idx < 0)
+		return alias_idx;
+
 	BUG_ON(alias_idx >= ARRAY_SIZE(gpio_chips));
 	if (gpio_chips[alias_idx])
 		return dev_err_probe(dev, -EBUSY, "%d slot is occupied.\n", alias_idx);