staging: iio: Fix dependencies for !HAS_IOMEM archs

Not every arch has io memory.
So, unbreak the build by fixing the dependencies.
Signed-off-by: NRichard Weinberger <richard@nod.at>
Acked-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/Kconfig

@@ -6,6 +6,7 @@ menu "Analog to digital converters"
 config AD7606
 	tristate "Analog Devices AD7606 ADC driver"
 	depends on GPIOLIB || COMPILE_TEST
+	depends on HAS_IOMEM
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	help