pinctrl: nuvoton: wpcm450: fix out of bounds write

Write into 'pctrl->gpio_bank' happens before the check for GPIO index
validity, so out of bounds write may happen.

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

Fixes: a1d1e0e ("pinctrl: nuvoton: Add driver for WPCM450")
Signed-off-by: Mikhail Kobuk <m.kobuk@ispras.ru>
Reviewed-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20230825101532.6624-1-m.kobuk@ispras.ru
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: Mikhail Kobuk

drivers/pinctrl/nuvoton/pinctrl-wpcm450.c

@@ -1062,13 +1062,13 @@ static int wpcm450_gpio_register(struct platform_device *pdev,
 		if (ret < 0)
 			return ret;
 
-		gpio = &pctrl->gpio_bank[reg];
-		gpio->pctrl = pctrl;
-
 		if (reg >= WPCM450_NUM_BANKS)
 			return dev_err_probe(dev, -EINVAL,
 					     "GPIO index %d out of range!\n", reg);
 
+		gpio = &pctrl->gpio_bank[reg];
+		gpio->pctrl = pctrl;
+
 		bank = &wpcm450_banks[reg];
 		gpio->bank = bank;