iio: Change ISA_BUS_API dependency to selection

The ISA_BUS_API Kconfig option enables the compilation of the ISA bus
driver. The ISA bus driver does not perform any hardware interaction,
and is instead just a thin layer of software abstraction to eliminate
boilerplate code common to ISA-style device drivers. Since ISA_BUS_API
has no dependencies and does not jeopardize the integrity of the system
when enabled, drivers should select it when the ISA bus driver
functionality is needed.

Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/iio/adc/Kconfig

@@ -698,7 +698,8 @@ config STM32_DFSDM_ADC
 
 config STX104
 	tristate "Apex Embedded Systems STX104 driver"
-	depends on PC104 && X86 && ISA_BUS_API
+	depends on PC104 && X86
+	select ISA_BUS_API
 	select GPIOLIB
 	help
 	  Say yes here to build support for the Apex Embedded Systems STX104

drivers/iio/counter/Kconfig

@@ -7,7 +7,8 @@ menu "Counters"
 
 config 104_QUAD_8
 	tristate "ACCES 104-QUAD-8 driver"
-	depends on PC104 && X86 && ISA_BUS_API
+	depends on PC104 && X86
+	select ISA_BUS_API
 	help
 	  Say yes here to build support for the ACCES 104-QUAD-8 quadrature
 	  encoder counter/interface device family (104-QUAD-8, 104-QUAD-4).

drivers/iio/dac/Kconfig

@@ -195,7 +195,8 @@ config AD7303
 
 config CIO_DAC
 	tristate "Measurement Computing CIO-DAC IIO driver"
-	depends on X86 && ISA_BUS_API
+	depends on X86 && (ISA_BUS || PC104)
+	select ISA_BUS_API
 	help
 	  Say yes here to build support for the Measurement Computing CIO-DAC
 	  analog output device family (CIO-DAC16, CIO-DAC08, PC104-DAC06). The