mmc: increse the max-frequency for read/write speed of emmc

Change-Id: I183ae6cdc0e0c6279bcfd27ed233d9796cda1152

Author: Andy3Kuo

arch/arm/boot/dts/rk3288-tinker-board.dtsi

@@ -187,7 +187,7 @@
 	num-slots = <1>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&emmc_clk &emmc_cmd &emmc_pwr &emmc_bus8>;
-	max-frequency = <100000000>;
+	max-frequency = <150000000>;
 	mmc-hs200-1_8v;
 	mmc-ddr-1_8v;
 	status = "okay";