arm64: dts: rockchip: slow down emmc freq for rock 5 itx

The current max-frequency 200000000 of emmc is not stable. When doing
heavy write there will be I/O Error. After setting max-frequency to
150000000 the emmc is stable under write.

Also remove property mmc-hs200-1_8v because we are already running at
HS400 mode.

Tested with fio command:
fio -filename=./test_randread -direct=1 -iodepth 1 -thread \
-rw=randwrite -ioengine=psync -bs=16k -size=1G -numjobs=10 \
-runtime=600 -group_reporting -name=mytest

Signed-off-by: Jianfeng Liu <liujianfeng1994@gmail.com>
Link: https://lore.kernel.org/r/20250228143341.70244-1-liujianfeng1994@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

Author: amazingfate

arch/arm64/boot/dts/rockchip/rk3588-rock-5-itx.dts

@@ -690,10 +690,9 @@
 
 &sdhci {
 	bus-width = <8>;
-	max-frequency = <200000000>;
+	max-frequency = <150000000>;
 	mmc-hs400-1_8v;
 	mmc-hs400-enhanced-strobe;
-	mmc-hs200-1_8v;
 	no-sdio;
 	no-sd;
 	non-removable;