rockchip: imply ADC and SARADC_ROCKCHIP for Rockchip SOCs

Enable the Rockchip SARADC driver for all Rockchip SoCs.

Note that the SARADC peripheral is available on all SoCs except the
RK3036 and RK3228.  However, as this is a DM-driver, enabling by
default will not cause any function problems (and can always be
changed from defconfig, if size is a concern).
Signed-off-by: NPhilipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: NDavid Wu <david.wu@rock-chips.com>

arch/arm/Kconfig

@@ -1115,6 +1115,8 @@ config ARCH_ROCKCHIP
 	imply FAT_WRITE
 	imply USB_FUNCTION_FASTBOOT
 	imply SPL_SYSRESET
+	imply ADC
+	imply SARADC_ROCKCHIP
 
 config TARGET_THUNDERX_88XX
 	bool "Support ThunderX 88xx"