clk: rockchip: add SCLK_DDRC id for rk3399 ddrc

Add the needed id for the ddr clock.
Signed-off-by: Lin Huang <hl@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

include/dt-bindings/clock/rk3399-cru.h

@@ -131,6 +131,7 @@
 #define SCLK_DPHY_RX0_CFG		165
 #define SCLK_RMII_SRC			166
 #define SCLK_PCIEPHY_REF100M		167
+#define SCLK_DDRC			168
 
 #define DCLK_VOP0			180
 #define DCLK_VOP1			181