ram: rk3328: use common sdram driver

RK3328 has a similar controller and phy with PX30, so we can use the
common driver for it and remove the duplicate codes.

Signed-off-by: YouMin Chen <cym@rock-chips.com>
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 f5a80b4..5f1ad51 100644
--- a/arch/arm/mach-rockchip/Kconfig
+++ b/arch/arm/mach-rockchip/Kconfig
@@ -115,6 +115,7 @@
 	select TPL_NEEDS_SEPARATE_TEXT_BASE if TPL
 	select TPL_NEEDS_SEPARATE_STACK if TPL
 	imply ROCKCHIP_COMMON_BOARD
+	imply ROCKCHIP_SDRAM_COMMON
 	imply SPL_ROCKCHIP_COMMON_BOARD
 	imply SPL_SERIAL_SUPPORT
 	imply TPL_SERIAL_SUPPORT