Input: gpio_keys - fix warning regarding uninitialized 'button' variable

Commit af906faabcf91eb1 ("Input: gpio_keys - fix warning regarding uninitialized
'irq' variable") introduced the following build warning:

drivers/input/keyboard/gpio_keys.c:625:16: warning: 'button' may be used uninitialized in this function [-Wmaybe-uninitialized]

Move the 'button' initialization to a proper location to avoid such warning.

Reported-by: Olof's autobuilder <[e-mail]>
Signed-off-by: Fabio Estevam <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/keyboard/gpio_keys.c

···
 		int gpio = -1;
 		enum of_gpio_flags flags;
 
+		button = &pdata->buttons[i++];
+
 		if (!of_find_property(pp, "gpios", NULL)) {
 			button->irq = irq_of_parse_and_map(pp, 0);
 			if (button->irq == 0) {
+				i--;
 				pdata->nbuttons--;
 				dev_warn(dev, "Found button without gpios or irqs\n");
 				continue;
···
 				return ERR_PTR(error);
 			}
 		}
-
-		button = &pdata->buttons[i++];
 
 		button->gpio = gpio;
 		button->active_low = flags & OF_GPIO_ACTIVE_LOW;