pinctrl: apple-gpio: fix flexible_array.cocci warnings

Zero-length and one-element arrays are deprecated, see
Documentation/process/deprecated.rst
Flexible-array members should be used instead.

Generated by: scripts/coccinelle/misc/flexible_array.cocci

CC: Joey Gouly <joey.gouly@arm.com>
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NJulia Lawall <julia.lawall@inria.fr>
Link: https://lore.kernel.org/r/alpine.DEB.2.22.394.2111271859250.2864@hadrienSigned-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-apple-gpio.c

@@ -37,7 +37,7 @@ struct apple_gpio_pinctrl {
 	struct pinctrl_desc pinctrl_desc;
 	struct gpio_chip gpio_chip;
 	struct irq_chip irq_chip;
-	u8 irqgrps[0];
+	u8 irqgrps[];
 };
 
 #define REG_GPIO(x)          (4 * (x))