arm64: dts: ti: k3-am64-main: Remove support for HS400 speed mode

AM64 SoC, does not support HS400 and HS200 is the maximum supported speed
mode[1]. Therefore, fix the device tree node to reflect the same.

[1] - https://www.ti.com/lit/ds/symlink/am6442.pdf
      (SPRSP56C – JANUARY 2021 – REVISED FEBRUARY 2022)

Fixes: 8abae93 ("arm64: dts: ti: Add support for AM642 SoC")
Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20220512064859.32059-1-a-govindraju@ti.com

arch/arm64/boot/dts/ti/k3-am64-main.dtsi

@@ -456,13 +456,11 @@
 		clock-names = "clk_ahb", "clk_xin";
 		mmc-ddr-1_8v;
 		mmc-hs200-1_8v;
-		mmc-hs400-1_8v;
 		ti,trm-icp = <0x2>;
 		ti,otap-del-sel-legacy = <0x0>;
 		ti,otap-del-sel-mmc-hs = <0x0>;
 		ti,otap-del-sel-ddr52 = <0x6>;
 		ti,otap-del-sel-hs200 = <0x7>;
-		ti,otap-del-sel-hs400 = <0x4>;
 	};
 
 	sdhci1: mmc@fa00000 {