Input: gpio-keys - fix possible NULL pointer dereference

bdata->button is used in gpio_check_button but never initialized.  Having a
device with debounce_interval != 0 without this patch resulted on an oops on
my machine.
Signed-off-by: NUwe Kleine-König <Uwe.Kleine-Koenig@digi.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

drivers/input/keyboard/gpio_keys.c

@@ -118,6 +118,7 @@ static int __devinit gpio_keys_probe(struct platform_device *pdev)
 		unsigned int type = button->type ?: EV_KEY;
 
 		bdata->input = input;
+		bdata->button = button;
 		setup_timer(&bdata->timer,
 			    gpio_check_button, (unsigned long)bdata);