gpio: davinci: Validate the obtained number of IRQs

Value of pdata->gpio_unbanked is taken from Device Tree. In case of broken
DT due to any error this value can be any. Without this value validation
there can be out of chips->irqs array boundaries access in
davinci_gpio_probe().

Validate the obtained nirq value so that it won't exceed the maximum
number of IRQs per bank.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: eb3744a2dd01 ("gpio: davinci: Do not assume continuous IRQ numbering")
Signed-off-by: Aleksandr Mishin <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-davinci.c

···
 	else
 		nirq = DIV_ROUND_UP(ngpio, 16);
 
+	if (nirq > MAX_INT_PER_BANK) {
+		dev_err(dev, "Too many IRQs!\n");
+		return -EINVAL;
+	}
+
 	chips = devm_kzalloc(dev, sizeof(*chips), GFP_KERNEL);
 	if (!chips)
 		return -ENOMEM;