iio: adc: ad7173: fix compiling without gpiolib

Fix compiling the ad7173 driver when CONFIG_GPIOLIB is not set by
selecting GPIOLIB to be always enabled and remove the #if.

Commit 031bdc8a ("iio: adc: ad7173: add calibration support") placed
unrelated code in the middle of the #if IS_ENABLED(CONFIG_GPIOLIB) block
which caused the reported compile error.

However, later commit 7530ed2a ("iio: adc: ad7173: add openwire
detection support for single conversions") makes use of the gpio regmap
even when we aren't providing gpio controller support. So it makes more
sense to always enable GPIOLIB rather than trying to make it optional.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202504220824.HVrTVov1-lkp@intel.com/


Fixes: 031bdc8a ("iio: adc: ad7173: add calibration support")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250422-iio-adc-ad7173-fix-compile-without-gpiolib-v1-1-295f2c990754@baylibre.com


Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>