iio: adc: Split AD7091R-5 config symbol

Split AD7091R-5 kconfig symbol into one symbol for the base AD7091R driver
and another one for the I2C interface AD7091R-5 driver.
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Link: https://lore.kernel.org/r/8cae37c611c1b0fe3faef7a4b8c4cc915eaeddc7.1703013352.git.marcelo.schmitt1@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/Kconfig

@@ -36,9 +36,13 @@ config AD4130
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad4130.
 
+config AD7091R
+	tristate
+
 config AD7091R5
 	tristate "Analog Devices AD7091R5 ADC Driver"
 	depends on I2C
+	select AD7091R
 	select REGMAP_I2C
 	help
 	  Say yes here to build support for Analog Devices AD7091R-5 ADC.

drivers/iio/adc/Makefile

@@ -7,7 +7,8 @@
 obj-$(CONFIG_AB8500_GPADC) += ab8500-gpadc.o
 obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
 obj-$(CONFIG_AD4130) += ad4130.o
-obj-$(CONFIG_AD7091R5) += ad7091r5.o ad7091r-base.o
+obj-$(CONFIG_AD7091R) += ad7091r-base.o
+obj-$(CONFIG_AD7091R5) += ad7091r5.o
 obj-$(CONFIG_AD7124) += ad7124.o
 obj-$(CONFIG_AD7192) += ad7192.o
 obj-$(CONFIG_AD7266) += ad7266.o