gpio-rb91x-key: add gc owner

For platform drivers themselves this is not needed. but for gpiochips,
it is to avoid module unload.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: openwrt/openwrt#23731
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>

Author: neheb

target/linux/ath79/files/drivers/gpio/gpio-rb91x-key.c

@@ -167,6 +167,7 @@ static int gpio_rb91x_key_probe(struct platform_device *pdev)
 	gc = &drvdata->gc;
 	gc->label = GPIO_RB91X_KEY_DRIVER_NAME;
 	gc->parent = dev;
+	gc->owner = THIS_MODULE;
 	gc->can_sleep = 1;
 	gc->base = -1;
 	gc->ngpio = GPIO_RB91X_KEY_NGPIOS;