iio: adc: ad4130: depend on GPIOLIB

Fixes undefined references to 'gpiochip_get_data' and
'devm_gpiochip_add_data_with_key'.
Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Reported-by: kernel test robot <lkp@intel.com>
Fixes: 62094060 ("iio: adc: ad4130: add AD4130 driver")
Link: https://lore.kernel.org/r/20221114133649.1737027-1-cosmin.tanislav@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/Kconfig

@@ -24,6 +24,7 @@ config AD_SIGMA_DELTA
 config AD4130
 	tristate "Analog Device AD4130 ADC Driver"
 	depends on SPI
+	depends on GPIOLIB
 	select IIO_BUFFER
 	select IIO_KFIFO_BUF
 	select REGMAP_SPI