RK809噪声，由于电压供应不对引起
microvolt = <3300000>;改为microvolt = <3000000>;后噪声消除了！
修改后的电压：
vcc3v0_pmu: LDO_REG4 {
regulator-always-on;regulator-boot-on;regulator-min-microvolt = <3000000>;regulator-max-microvolt = <3000000>;regulator-name = "vcc3v0_pmu";regulator-state-mem {
regulator-on-in-suspend;regulator-suspend-microvolt = <3000000>;};
};
原始电压：
vcc3v0_pmu: LDO_REG4 {
regulator-always-on;regulator-boot-on;regulator-min-microvolt = <3300000>;regulator-max-microvolt = <3300000>;regulator-name = "vcc3v0_pmu";regulator-state-mem {
regulator-on-in-suspend;regulator-suspend-microvolt = <3300000>;};
};