rockchip: rk3188: Migrate to use common board file

Use common board file for board_init() and board_late_init(),
for Rockchip SoCs have very similar process.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/Kconfig b/arch/arm/mach-rockchip/Kconfig
index a62ce44..86b01df 100644
--- a/arch/arm/mach-rockchip/Kconfig
+++ b/arch/arm/mach-rockchip/Kconfig
@@ -38,6 +38,7 @@
 	select SPL_ROCKCHIP_EARLYRETURN_TO_BROM
 	select SPL_ROCKCHIP_BACK_TO_BROM
 	select BOARD_LATE_INIT
+	imply ROCKCHIP_COMMON_BOARD
 	imply SPL_ROCKCHIP_COMMON_BOARD
 	help
 	  The Rockchip RK3188 is a ARM-based SoC with a quad-core Cortex-A9