leds: gpio: Annotate struct gpio_leds_priv with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct gpio_leds_priv.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocciSigned-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230915201003.never.148-kees@kernel.orgSigned-off-by: Lee Jones <lee@kernel.org>

drivers/leds/leds-gpio.c

@@ -142,7 +142,7 @@ static int create_gpio_led(const struct gpio_led *template,
 
 struct gpio_leds_priv {
 	int num_leds;
-	struct gpio_led_data leds[];
+	struct gpio_led_data leds[] __counted_by(num_leds);
 };
 
 static struct gpio_leds_priv *gpio_leds_create(struct platform_device *pdev)