Limit Nintendo Switch's external SD SDHCI bus clock speed.

This will fix Nintendo Switch does not load rootfs with some
"incompatible" SD cards, which supports UHS SDR104 speed.

So, this patch will solve this problem by limiting bus speed
to Switch's hardware can handle.

By experimentally obtained experience, 150MHz works fine with
64GB Samsung EVO+ microSD cards

arch/arm64/boot/dts/nvidia/tegra210-nintendo-switch.dts

@@ -941,6 +941,7 @@
 	sdhci@700b0000 {
 		status = "okay";
 		bus-width = <4>;
+		max-frequency = <150000000>;
 
 		cd-gpios = <&gpio TEGRA_GPIO(Z, 1) GPIO_ACTIVE_LOW>;
 		power-gpios = <&gpio TEGRA_GPIO(E, 4) GPIO_ACTIVE_HIGH>;