dts: arm64: rk3399: add max-frequency for sdhci

Add 'max-frequency' for sdhci node for clock init.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>

arch/arm/dts/rk3399.dtsi

@@ -188,6 +188,7 @@
 		interrupts = <GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>;
 		assigned-clocks = <&cru SCLK_EMMC>;
 		assigned-clock-rates = <200000000>;
+		max-frequency = <200000000>;
 		clocks = <&cru SCLK_EMMC>, <&cru ACLK_EMMC>;
 		clock-names = "clk_xin", "clk_ahb";
 		phys = <&emmc_phy>;