rockchip: rk3399: enable SPL_SERIAL_SUPPORT and SPL_DRIVERS_MISC_SUPPORT via Kconfig

SPL_SERIAL_SUPPORT and SPL_DRIVERS_MISC_SUPPORT were previously
enabled through rk3399_common.h.  This change implies these options
through Kconfig.

These need to always be active for the RK3399, as follows:
 - SPL_SERIAL_SUPPORT is needed to pass the SPL build
 - SPL_DRIVERS_MISC_SUPPORT is needed to pass the SPL build

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/arch/arm/mach-rockchip/Kconfig b/arch/arm/mach-rockchip/Kconfig
index bb44c61..c924613 100644
--- a/arch/arm/mach-rockchip/Kconfig
+++ b/arch/arm/mach-rockchip/Kconfig
@@ -82,6 +82,8 @@
 	select SUPPORT_SPL
 	select SPL
 	select SPL_SEPARATE_BSS
+	select SPL_SERIAL_SUPPORT
+	select SPL_DRIVERS_MISC_SUPPORT
 	select ENABLE_ARM_SOC_BOOT0_HOOK
 	select DEBUG_UART_BOARD_INIT
 	help