iio: adc: Fix exynos_adc dependencies

EXYNOS_ADC shouldn't only depend on OF. It is useless on architectures
other than Exynos so it should depend on ARCH_EXYNOS (which implies
OF.)
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/Kconfig

@@ -118,7 +118,7 @@ config AT91_ADC
 
 config EXYNOS_ADC
 	bool "Exynos ADC driver support"
-	depends on OF
+	depends on ARCH_EXYNOS || (OF && COMPILE_TEST)
 	help
 	  Core support for the ADC block found in the Samsung EXYNOS series
 	  of SoCs for drivers such as the touchscreen and hwmon to use to share