iio: adc: ep93xx: Enable wider build testing with COMPILE_TEST

It is useful to be able to build this driver without needing
to build support for ARCH_EP93XX.

Also add an explicit dependency on HAS_IOMEM so we have
devm_platform_ioremap_resource() etc available.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Cc: Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Link: https://lore.kernel.org/r/20221231144128.489810-1-jic23@kernel.org

drivers/iio/adc/Kconfig

@@ -441,7 +441,8 @@ config ENVELOPE_DETECTOR
 
 config EP93XX_ADC
 	tristate "Cirrus Logic EP93XX ADC driver"
-	depends on ARCH_EP93XX
+	depends on ARCH_EP93XX || COMPILE_TEST
+	depends on HAS_IOMEM
 	help
 	  Driver for the ADC module on the EP93XX series of SoC from Cirrus Logic.
 	  It's recommended to switch on CONFIG_HIGH_RES_TIMERS option, in this