iio: adc: ad7091r8: Fix error code in ad7091r8_gpio_setup()

There is a copy and paste error so it accidentally returns ->convst_gpio
instead of ->reset_gpio. Fix it.

Fixes: 0b76ff46c463 ("iio: adc: Add support for AD7091R-8")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Link: https://lore.kernel.org/r/fd905ad0-6413-489c-9a3b-90c0cdb35ec9@moroto.mountain
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: Add support for AD7091R-8

Add support for Analog Devices AD7091R-2, AD7091R-4, and AD7091R-8
low power 12-Bit SAR ADCs with SPI interface.
Extend ad7091r-base driver so it can be used by the AD7091R-8 driver.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Link: https://lore.kernel.org/r/09d1d1c4b39cecc528488efac6094233715f5659.1703013352.git.marcelo.schmitt1@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>